Watchman (6)
I believe the answer is:
sentry
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">watchman</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that sentry is a type of watchman)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sentry that I've seen before include "Watchman" , "One who stands guard" , "Mil. guard" , "Sentinel, watch" , "Guard on watch" .)