Piece trimmed is level (3)
I believe the answer is:
par
'is level' is the definition.
(I have seen 'Accepted level ' mean 'par' so perhaps 'level' could also mean 'par')
'piece trimmed' is the wordplay.
'piece' becomes 'part' (synonyms).
'trimmed' means to remove the last letter (the final letter is trimmed off).
'part' with its final letter removed is 'PAR'.
(Other definitions for par that I've seen before include "Normal number of strokes for a hole at golf" , "A number of golfing" , "Average or normal score" , "standard for course" , "Target score (golf)" .)