It may qualify as part of agreement (7)
I believe the answer is:
proviso
'agreement' is the definition.
The definition and answer 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?
'it may qualify as part of' is the wordplay.
I cannot really understand how this works, but
'as' could be 'so' (I've seen this in other clues) and 'so' is located in the answer.
'of' could be 'o' and 'o' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for proviso that I've seen before include "Rider" , "Stipulated condition" , "Condition attached to an agreement" , "Something insisted upon as part of an agreement" , "Condition, qualification" .)