Small sea creature (8)
I believe the answer is:
nautilus
'small sea creature' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for nautilus that I've seen before include "Captain Nemo's submarine" , "Nemo's sub (Verne)" , "craft in fiction" , "Creature of deep" , "Usual tin for a small sea creature" .)