Small sea creature (8)
I believe the answer is:
nautilus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">small sea creature</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)