Small piece, incomplete, gets criticism (4)
I believe the answer is:
flak
'criticism' is the definition.
(I've seen this before)
'small piece incomplete' is the wordplay.
'small piece' becomes 'flake'.
'incomplete' means to remove the last letter.
'flake' with its last letter taken away is 'FLAK'.
'gets' acts as a link.
(Other definitions for flak that I've seen before include "heated disagreement" , "Shooting" , "Brickbats" , "Anti-aircraft fire - strong criticism" , "complaints" .)