Region surrounding new stadium (5)
I believe the answer is:
arena
'stadium' is the definition.
(eg a sports arena)
'region surrounding new' is the wordplay.
'region' becomes 'area' (area is a kind of region).
'surrounding' indicates putting letters inside.
'new' becomes 'n' (abbreviation as in New Testament NT).
'area' enclosing 'n' is 'ARENA'.
(Other definitions for arena that I've seen before include "Where gladiators fought" , "Scene of open conflict" , "Wembley, say" , "Stadium - battlefield" , "Gladiatorial venue" .)