Seabird's utterly essential for a kebab (4)
I believe the answer is:
skua
'seabird's' is the definition.
(type of seabird)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for skua that I've seen before include "Large predatory bird" , "Brownish sea bird" , "Arctic seabird" , "One preying on gulls" , "Predatory northern seabird" .)