Munch or chew noisily (5)
I believe the answer is:
chomp
This clue is a double definition.
'munch' is the first definition.
(I've seen this before)
'chew noisily' is the second definition.
(I've seen this in another clue)
(Other definitions for chomp that I've seen before include "Munch noisily (colloq.)" , "Chew" , "For crunch" .)