Navy officer (7)
I believe the answer is:
admiral
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">navy officer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that admiral is a type of flag officer)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for admiral that I've seen before include "Naval officer of high rank" , "Highest naval rank" , "Red butterfly at sea?" , "Navy chief" , "[NELSON] perhaps" .)