Senior naval officer (7)
I believe the answer is:
admiral
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">senior naval officer</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 admiral that I've seen before include "High-ranking naval officer like Nelson" , "Senior officer; mad liar (anag.)" , "Navy bigwig" , "Naval high-up" , "Highest naval rank" .)