Stuff made with cold butter? (4)
I believe the answer is:
cram
'stuff' is the definition.
(cramming is a kind of stuffing)
'with cold butter?' is the wordplay.
'with' is a charade indicator (letters next to each other).
'cold' becomes 'c' (eg on taps).
'butter?' becomes 'ram' (I've seen this in other clues).
'c' put next to 'ram' is 'CRAM'.
'made' acts as a link.
(Other definitions for cram that I've seen before include "Study intensively" , "Study hard for exam" , "Quickly learn - stuff" , "A crush" , "Feed greedily" .)