Black-and-white sea creature (4)
I believe the answer is:
orca
'black-and-white sea creature' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for orca that I've seen before include "grampus" , "27 [WHALE]" , "Marine creature" , "Killer whales" , "swimmer in black and white" .)