Part of stadium for bear (5)
I believe the answer is:
stand
I believe this clue is a double definition.
'part of stadium' is the first definition.
(I know that stand is part of arena)
'for bear' is the second definition.
(bear can mean to stand or endure)
(Other definitions for stand that I've seen before include "Sit here at a sports event" , "Support" , "Get to one's feet" , "station" , "Watch and do nothing to help" .)