This poem's rhyme scheme may be AAAA, ABAB or ABBA (8)
I believe the answer is:
quatrain
'this poem's rhyme' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for quatrain that I've seen before include "Four-lined verse" , "Stanza or poem of four lines" , "Type of verse with four lines" , "Poem of four lines found in a quart" , "Poet may write it" .)