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