Tropical eel (5)
I believe the answer is:
moray
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">tropical eel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for moray that I've seen before include "Predator eel" , "Firth" , "seen snaking near the coast?" , "One fish" , "is fishy" .)