Operating room (7)
I believe the answer is:
theatre
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">operating room</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 theatre that I've seen before include "Major area of military activity" , "Where dramas may be" , "Space for drama" , "stage productions" , "Drama in general" .)