Roman sea god (7)
I believe the answer is:
neptune
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">roman sea god</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for neptune that I've seen before include "Planet, identified 1846" , "Poseidon" , "Roman god of the sea, with trident" , "Roman sea god - planet" , "one of the Planets" .)