District containing new sports venue (5)
I believe the answer is:
arena
'sports venue' is the definition.
(I've seen this before)
'district containing new' is the wordplay.
'district' becomes 'area' (I've seen this before).
'containing' is an insertion indicator.
'new' becomes 'n'.
'area' placed around 'n' is 'ARENA'.
(Other definitions for arena that I've seen before include "Performance venue" , "Performance space" , "Contest venue" , "sports ground" , "Place or scene of activity" .)