Sister nobody listened to (3)
I believe the answer is:
nun
'sister' is the definition.
(sister is a term of address for a nun)
'nobody listened to' is the wordplay.
'nobody' becomes 'none' (not a single person).
'listened to' shows a homophone (sound like).
'none' is a homophone of 'NUN'.
(Other definitions for nun that I've seen before include "Joshua's father" , "Mother Teresa, maybe" , "Mother Superior, perhaps" , "Black and white pigeon" , "Religious sister" .)