Ring a district round the north (5)
I believe the answer is:
arena
'ring' is the definition.
(ring is a kind of arena or venue)
'a district round the north' is the wordplay.
'a district' becomes 'area' (I've seen this before).
'round' is an insertion indicator.
'the north' becomes 'N' (abbreviation).
'area' enclosing 'n' is 'ARENA'.
(Other definitions for arena that I've seen before include "Gladiatorial ring" , "Area of endeavour" , "Place of public contest" , "Place for public events" , "Playing field or boxing ring" .)