Hidden gunman (6)
I believe the answer is:
sniper
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">hidden gunman</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 sniper that I've seen before include "One who criticises" , "Military marksman" , "One shoots from a concealed place" , "Lone rifleman" , "Concealed shooter" .)