The address of a single person (9)
I believe the answer is:
monologue
'the address' 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 don't see?
'a single person' is the wordplay.
'a single' becomes 'mono' (prefix meaning single).
'person' becomes 'logue' (I am not sure about this - if you are sure you should believe this answer much more).
'mono'+'logue'='MONOLOGUE'
'of' is the link.
Can you help me to learn more?
(Other definitions for monologue that I've seen before include "Long and tedious speech" , "speaking without interruption" , "Soliloquy" , "Long dramatic speech by a single actor" , "Long uninterrupted speech" .)