London exhibition hall (7)
I believe the answer is:
olympia
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">london exhibition hall</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for olympia that I've seen before include "Dublin theatre" , "London venue - Greek Games site" , "Greek district" , "Chief sanctuary of Zeus" , "venue for godly sports" .)