Area near crumbling stadium (5)
I believe the answer is:
arena
'stadium' is the definition.
(eg a sports arena)
'area near crumbling' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'crumbling' is an anagram indicator.
'near' with letters rearranged gives 'rena'.
'a'+'rena'='ARENA'
(Other definitions for arena that I've seen before include "Sphere of intense activity" , "Field of battle" , "Central area in sports stadium" , "where there's competition" , "Part of a stadium" .)