Cook small fish (3)
I believe the answer is:
fry
This clue is a double definition.
'cook' is the first definition.
(frying is a type of cooking)
'small fish' is the second definition.
(I've seen this before)
(Other definitions for fry that I've seen before include "Christopher" , "Cook in fat; young fish" , "woman of note" , "Writer" , "Newly-hatched fishes for the pan?" .)