US Department of Defense (8)
I believe the answer is:
pentagon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">us department of defense</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 pentagon that I've seen before include "top brass" , "Headquarters of USA Department of Defence" , "Figure in plane" , "Headquarters of the US Defense Department" , "rectangle snipped at one corner?" .)