Dark shade of blue (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">dark shade of blue</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 navy that I've seen before include "Dark shade of blue" , "Shade of the marine forces" , "Colour; fighting force" , "Marine force" , "Senior service" .)