Lookout (6)
I believe the answer is:
sentry
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lookout</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that lookout can be written as sentry)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for sentry that I've seen before include "One keeps watch" , "One who stands guard" , "Military guard" , "Look-out, guard" , "Person standing watch" .)