Sea-going vessel (4)
I believe the answer is:
ship
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sea-going vessel</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 ship that I've seen before include "See 18" , "In a word, final indication of rank or position" , "part of navy" , "Sea-going craft" , "Vessel that carries passengers or freight" .)