Spare item cut (4)
I believe the answer is:
thin
'spare' is the definition.
(similar in meaning)
'item cut' is the wordplay.
'item' becomes 'thing' (both can mean an object).
'cut' means to remove the last letter.
'thing' with its final letter taken off is 'THIN'.
(Other definitions for thin that I've seen before include "Slender, narrow" , "(Of smile) weak, forced" , "Unconvincing" , "Meagre" , "Sparse; not dense" .)