Cockney warms food (4)
I believe the answer is:
eats
This clue is a double definition.
'cockney warms' is the first definition.
('heats' - I've seen this in another clue - said with a cockney accent, dropping the 'H')
'food' is the second definition.
(eats can mean food)
(Other definitions for eats that I've seen before include "Commonly, they eliminate" , "Tuck" , "snacks" , "Consumes with teas" , "bits of food" .)