Fish eaten on quay (7)
I believe the answer is:
haddock
'fish' is the definition.
(haddock is a kind of fish)
'eaten on quay' is the wordplay.
'eaten' becomes 'had' (e.g. an ice cream was had by Jane).
'on' is a charade indicator (letters next to each other).
'quay' becomes 'dock' (I've seen this before).
'had'+'dock'='HADDOCK'
(Other definitions for haddock that I've seen before include "Fish similar to but smaller than cod" , "ish" , "Fish like cod but smaller" , "Fish, often smoked" , "Popular food fish" .)