Head cook brings in sushi at last (5)
I believe the answer is:
chief
'head' is the definition.
('chief' can be a synonym of 'head')
'cook brings in sushi at last' is the wordplay.
'cook' becomes 'chef' (chef is a kind of cook**).
'brings in' indicates putting letters inside.
'at last' says to take the final letters.
The final letter of 'sushi' is 'i'.
'chef' placed around 'i' is 'CHIEF'.
(Other definitions for chief that I've seen before include "Main" , "Leader; most important" , "Head of a native American tribe" , "cardinal" , "Person in charge, head" .)