Space around Northern stadium (5)
I believe the answer is:
arena
'stadium' is the definition.
(eg a sports arena)
'space around northern' is the wordplay.
'space' becomes 'area' (I've seen this before).
'around' is an insertion indicator.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'area' placed around 'n' is 'ARENA'.
(Other definitions for arena that I've seen before include "Area of activity, boxing perhaps" , "Entertainments venue" , "Area surrounded by seating, for sports, etc." , "Cheap Prom tickets" , "Show ring" .)