Auditorium; sports venue (5)
I believe the answer is:
arena
I believe this is a double definition.
'auditorium' is the first definition.
(I've seen this before)
'sports venue' is the second definition.
(I've seen this in another clue)
(Other definitions for arena that I've seen before include "Place or scene of activity" , "Performance space" , "Place of great activity" , "Sporting enclosure" , "Battleground" .)