Surprisingly, perhaps, it may be French (6)
I believe the answer is:
polish
'french' is the definition.
The answer and definition can be both related to communication as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for polish that I've seen before include "Brush up" , "See 1" , "Substance used to produce shine" , "Europeans" , "tongue" .)