Japanese fighter (5)
I believe the answer is:
ninja
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">japanese fighter</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 ninja that I've seen before include "Assassin from Japan" , "Feudal assassin" , "Teenage Mutant -- Turtles (TV/film)" , "Assassins" , "old mercenary" .)