Opponent eating large ice (4)
I believe the answer is:
floe
'ice' is the definition.
(thesaurus)
'opponent eating large' is the wordplay.
'opponent' becomes 'foe' (I've seen this before).
'eating' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'foe' going around 'l' is 'FLOE'.
(Other definitions for floe that I've seen before include "Flat mass of sea ice" , "Floating flat mass of ice" , "Frozen field" , "A field of floating ice" , "Broken piece of pack-ice" .)