Trimmed beef, say (4)
I believe the answer is:
mown
'trimmed' is the definition.
(thesaurus)
'beef say' is the wordplay.
'beef' becomes 'moan' (I've seen this before).
'say' shows a homophone (sound like).
'moan' sounds like 'MOWN'.
(Other definitions for mown that I've seen before include "Cut down with a blade" , "Block of cast metal" , "(Of grass) cut" .)