Of warships (5)
I believe the answer is:
naval
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">of warships</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 naval that I've seen before include "Relating to marine force" , "Of seaborne forces" , "Relating to nautical defence force" , "Maritime" , "To do with the marine branch of an army" .)