Partly eaten chips or fish (5)
I believe the answer is:
tench
'fish' is the definition.
(tench is a kind of fish)
'partly eaten chips or' is the wordplay.
'partly' indicates a hidden word (part of the clue is used).
'TENCH' is hidden within 'eaten chips or'.
(Other definitions for tench that I've seen before include "Swimmer" , "catch" , "Freshwater fish" , "something fishy" , "Fish of the carp family" .)