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' says the answer is hidden in the clue (part of the clue is used).
'TENCH' is hidden in the letters of 'eaten chips or'.
(Other definitions for tench that I've seen before include "Swimmer" , "catch" , "Freshwater fish" , "something fishy" , "Fish of the carp family" .)