Occupy in large numbers (7)
I believe the answer is:
overrun
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">occupy in large numbers</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 overrun that I've seen before include "Infest; carry beyond the limit" , "Invade - exceed time limit" , "Go beyond (time/budget)" , "Exceed (cost estimate)" , "Occupy (a place) in large numbers" .)