Defensive ditch
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">defensive ditch</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for moat that I've seen before include "A deep water-filled ditch around a castle" , "Defensive water" , "Ditch dug to protect a castle" , "Trench around fortifications" , "defensive construction" .)