Defensive wall (7)
I believe the answer is:
bulwark
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">defensive wall</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for bulwark that I've seen before include "Fortification - side of ship above deck" , "Rampart" , "Defensive wall" , "Buttress" , "defence" .)