Playing area near a ground (5)
I believe the answer is:
Here is my best explanation:
'a ground' is the definition.
'playing area near' is the subsidiary indication.
'playing' is an anagram indicator.
'area' becomes 'a' (maths abbreviation).
'anear' is an anagram of 'arena'.
(Other definitions for arena that I've seen before include "Centre of an amphitheatre", "Ring; stage", "Amphitheatre's central space", "Ring; stadium", "place for the audience", "Battleground", "Field of combat", "Place of activity, especially conflict", "Boxing ring" and "Scene of gladiatorial contest, perhaps".)