Instrument for serving up in cocoa butter (4)
I believe the answer is:
tuba
'instrument' is the definition.
(tuba is a kind of instrument)
'serving up in cocoa butter' is the wordplay.
'serving up' says the letters should be written backwards.
'in' says the answer is hidden in the clue.
'abut' is hidden within 'cocoa butter'.
'abut' backwards is 'TUBA'.
'for' is the link.
(Other definitions for tuba that I've seen before include "Brassy thing" , "Player" , "member of band" , "Brass "oompah" instrument" , "part of 14 [ORCHESTRA] ?" .)