Couple trim, by the sound of it? (4)
I believe the answer is:
pair
'couple' is the definition.
(synonyms)
'trim by the sound of it?' is the wordplay.
'trim' becomes 'pare' (synonyms).
'by the sound of it?' indicates a 'sounds like' (homophone) clue.
'pare' is a homophone of 'PAIR'.
(Other definitions for pair that I've seen before include "Duo" , "2" , "item" , "Two of a kind, as in cards" , "flight of stairs" .)