She makes not a single sound! (3)
I believe the answer is:
nun
'a single sound' is the definition.
The definition and answer can be both related to communication as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'she makes not' is the wordplay.
'she makes' becomes 'n' (I can't justify this - if you can you should believe this answer much more).
'not' becomes 'un' (I've seen this in other clues).
'n'+'un'='NUN'
Can you help me to learn more?
(Other definitions for nun that I've seen before include "She's a member of a religious community" , "Domestic fancy pigeon" , "A palindromic holy woman" , "Female in religious order" , "Member of convent" .)