Munch on cold chop (4)
I believe the answer is:
chew
'munch' is the definition.
(thesaurus)
'on cold chop' is the wordplay.
'on' says to put letters next to each other.
'cold' becomes 'c' (eg on taps).
'chop' becomes 'hew' (I've seen this in other clues**).
'c' next to 'hew' is 'CHEW'.
(Other definitions for chew that I've seen before include "Treat for dog" , "Munch" , "Bite and grind food in the mouth" , "What gossips do to fat" , "bit of tobacco" .)