Low wall (7)
I believe the answer is:
parapet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">low wall</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 parapet that I've seen before include "Wall edging a roof or bridge" , "low bank" , "Protective cover" , "Low protective wall along edge of roof or bridge" , "defensive position" .)