Cook endless seabird stew (6)
I believe the answer is:
braise
'cook' is the definition.
(braising is a kind of cooking)
'endless seabird stew' is the wordplay.
'endless' means to remove the last letter.
'stew' is an anagram indicator.
'seabird' with its final letter taken off is 'seabir'.
'seabir' with letters rearranged gives 'BRAISE'.
(Other definitions for braise that I've seen before include "Cook by stewing" , "Fry and then stew (food)" , "Stew in a closed pan" , "Fry then stew (meat)" , "Cook slowly with little water in closed container" .)