Cook a lot of fish (3)
I believe the answer is:
fry
'cook' is the definition.
(fry cook is a kind of cook)
'a lot of fish' is the wordplay.
'a lot' means to remove the first letter (I've seen 'a lot of' mean this).
'fish' becomes 'ry' (I can't explain this - if you can you should believe this answer much more).
'of' with its first letter removed is 'f'.
'f'+'ry'='FRY'
Can you help me to learn more?
(Other definitions for fry that I've seen before include "Newly-hatched fish" , "Cook small fish this way" , "young children" , "Quaker Elizabeth's" , "woman of note" .)