Playing field or boxing ring (5)
I believe the answer is:
arena
This clue is a double definition.
'playing field' is the first definition.
(arena is a kind of playing field)
'boxing ring' is the second definition.
(I've seen this before)
(Other definitions for arena that I've seen before include "place for sporting contest" , "Action space in centre of amphitheatre" , "Sphere of intense activity" , "Performance venue" , "Contest venue" .)