Would you say the "dharma" explains "dharmas"

The word "dhamma" is defined at length by the Pali English Dictionary. Per that definition, the word "element" can be used in the sense of "a dhamma", as a part of the Dhamma and not in the sense of the "four elements".

The Buddha does discuss the four elements, but although translators avail themselves of the word "element", it actually comes from a different Pali word, "dhatu".

SN14.30:1.4: Pathavīdhātu, āpodhātu, tejodhātu, vāyodhātu—
SN14.30:1.4: The elements of earth, water, fire, and air.

Unfortunately, the translation of two different Pali terms as "element" can lead to some confusion between a "part of the teaching" and the "four elements". To avoid such confusion, it is useful to learn a bit of Pali to understand the full meaning of the suttas.

The Buddha taught the Four Noble Truths: the existence of suffering, the origin of suffering, the end of suffering and the path that leads to the end of suffering. They are all real and true.

As we can see from the dictionary, the word "dhamma" has a tremendous scope and specific meanings according to context. That breadth of meaning actually makes it difficult to make statements about dhamma explaining dhamma. Such statements tend to sound a bit like "does truth explain truth?"

I'm not sure what you mean exactly by "suchness". Perhaps you meant what the teachings refer to as "present knowledge":

SN12.33:11.1: A noble disciple understands choices, their origin, their cessation, and the practice that leads to their cessation. This is their knowledge of the present phenomenon.
SN12.33:11.2: With this present phenomenon that is seen, known, immediate, attained, and fathomed, they infer to the past and future.
SN12.33:12.1: Whatever ascetics and brahmins in the past directly knew choices, their origin, their cessation, and the practice that leads to their cessation, all
of them directly knew these things in exactly the same way that I do now.
SN12.33:13.1: Whatever ascetics and brahmins in the future will directly know choices, their origin, their cessation, and the practice that leads to their cessation, all of them will directly know these things in exactly the same way that I do now.
SN12.33:13.2: This is their inferential knowledge.
SN12.33:14.1: A noble disciple has purified and cleansed these two knowledges—
SN12.33:14.2: knowledge of the present phenomena, and inferential knowledge.

In a sense, the Dhamma may be understood as the teaching that our "windshields are dirty". The dirtiness obscure our vision and results in much suffering. When we clean our windshields, we can see things as they are.

ud1.10:8.2: ‘In the seen will be merely the seen; in the heard will be merely the heard; in the thought will be merely the thought; in the known will be merely the known.’

The teaching of the Sublime Buddha explains Suffering, it's cause, it's ending and the way of conduct to bring itjs ending about, good householder. It's not a philosophy busy and eager to explain, defend and uphold it self and can be acknowledged and seen just by those doing the task, good householder. It's not thought for the sake of building ones house or open to be pulled into it for the sake of maintain ones stand but to removes it's roof, walls and fundation. It's for the sake to step over to real.

when expressed in the singular, the declensions of dhamma mean truth, justice or essential nature. when it is discussed it has the meaning of dogma, doctrine or teaching.

when in the plural, the declensions of dhamma have the meaning of phenomena, things, or elements. as in sabbe dhammā anattā, all phenomena are impersonal

In Pali, the word for 'element' is 'dhatu'. There are numerous suttas about the elements, such as MN 115, MN 140, SN 14.12, SN 14.15, Iti 44, etc.

The word 'dhatu' appears to have the same linguistic root as the word 'dhamma', meaning to 'uphold':

The Sanskrit dhatu is derived from a verb meaning to hold.

Encyclopedia of Buddhism

The word ‘Dhatu’ is derived from the verb ‘Dha’ (धा) which means to hold.

धारणात् धातवः |

dhāraṇāt dhātavaḥ |

The matters which hold the body are termed as Dhatu.

In general, it is a term signifying bodily fluids and tissues.

Dharmawiki

The word ‘dhatu’ is derived from the word root “Dha” by adding suffix “Tun”. The derivation of the word is as follows-

“डु धाञ धारणपोषणयोः”- meaning that which sustains and nourishes.

In general, the Sanskrit word conveys the meaning of a component, constituent, elementary substance, verbal, grammatical root or a metal.

Monier-Williams Sanskrit-English Dictionary, 1899

The word dharma has roots in the Sanskrit dhr-, which means to hold or to support, and is related to Latin firmus (firm, stable). From this, it takes the meaning of "what is established or firm", and hence "law". It is derived from an older Vedic Sanskrit n-stem dharman-, with a literal meaning of "bearer, supporter", in a religious sense conceived as an aspect of Rta.

Wikipedia

Ved. dharma & dharman, the latter a formation like karman (see kamma for expln of subj. & obj. meanings); dhṛ; (see dhāreti) to hold support: that which forms a foundation and upholds constitution. Cp. Gr. χρόνος, Lat. firmus & fretus Lith. derme (treaty), cp. also Sk. dhariman form, constitution perhaps = Lat. forma, E. form

PTS Pali English Dictionary

It was once explained to me the word 'dhatu' means 'that which upholds itself'; therefore being similar to the Pali Abhidhamma term 'sabhava'.

In short, it appears the word 'dhatu' ('element') is only used in one way in the Pali Sutta, namely, referring to a discrete natural thing, such as the element of earth, the element of water, the element of sensuality, the element of ignorance, the element of Nibbana, the elements forming the unique mental disposition of an individual, etc.

In contrast, the term 'dhamma' is used in myriad ways in the Pali Suttas however each way contains the inherent meaning of something that 'upholds' life, both physically (such as food, oxygen, water & sunlight) & mentally (such as stopping the mind from falling in the lower realms). Therefore, the word 'dhamma' in the Pali Suttas, dependent upon context, can mean:

• Thing/phenomena
• Law/truth/reality
• Teaching/doctrine
• Practice/path/duty
• Result of practice

You may refer to this ancient blog: The word ‘dhamma’ in context.

The term dhamma has multiple meanings in Buddhism. Dhamma is defined in the accesstoinsight.org glossary page as:

dhamma [Skt. dharma]:(1) Event; a phenomenon in and of itself; (2) mental quality; (3) doctrine, teaching; (4) nibbāna. Also, principles of behavior that human beings ought to follow so as to fit in with the right natural order of things; qualities of mind they should develop so as to realize the inherent quality of the mind in and of itself. By extension, "Dhamma" (usu. capitalized) is used also to denote any doctrine that teaches such things. Thus the Dhamma of the Buddha denotes both his teachings and the direct experience of nibbāna, the quality at which those teachings are aimed.

The first sense - dhamma as an event or phenomena, can apply to "thing" as well. I guess this is what you meant by "element", and not "dhatu".

dhātu: Element; property, impersonal condition. The four physical elements or properties are earth (solidity), water (liquidity), wind (motion), and fire (heat). The six elements include the above four plus space and consciousness.

If you want to know more about Dhamma, the doctrine and teachings of the Buddha, see this page.

If you want to know more about dhamma (mental quality or mental object), the fourth foundation of mindfulness, see this page, this page and the Satipatthana Sutta.

So, you can say that Dhamma (the teachings) explain dhamma (the mental objects) in the Satipatthana Sutta.