Like a sense of form? (5)
I believe the answer is:
sixth
'form?' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe you can see an association between them that I can't see?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sixth that I've seen before include "Musical interval from A to F, say" , "fraction" , "ordinal" , "Beaten by five" .)