Language unit's invitation to get in touch? (7)
I believe the answer is:
phoneme
'in touch?' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Maybe there's an association between them I don't understand?
'language unit's invitation' is the wordplay.
'language unit' becomes 'phone' (phone is a kind of language unit).
'invitation' becomes 'me' (I can't justify this - if you can you should give a lot more credence to this answer).
'phone'+'me'='PHONEME'
'to get' is the link.
(Other definitions for phoneme that I've seen before include "Unit of spoken sound" , "Small bit of speech" , "minimal piece of speech" , "distinctive sound" .)