Relating to warships (5)
I believe the answer is:
naval
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">relating to warships</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 naval that I've seen before include "Relating to marine force" , "Relates to nautical defence force" , "Relating to sea forces" , "Relating to the Senior Service" , "Of seaborne forces" .)