Trim couple heard (4)
I believe the answer is:
pare
'trim' is the definition.
(I know that trim can be written as pare)
'couple heard' is the wordplay.
'couple' becomes 'pair' (synonyms).
'heard' shows a homophone (sound like).
'pair' is a homophone of 'PARE'.
(Other definitions for pare that I've seen before include "Strip the skin from" , "Remove the skin from" , "Trim off in layers" , "Decrease gradually" , "Cut down gradually" .)