She makes not a single sound! (3)
I believe the answer is:
nun
'she' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'not a single sound' is the wordplay.
'not a single' becomes 'none' (not one).
'sound' indicates a 'sounds like' (homophone) clue.
'none' is a homophone of 'NUN'.
'makes' acts as a link.
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" .)