Running near a stadium (5)
I believe the answer is:
arena
'stadium' is the definition.
(eg a sports arena)
'running near a' is the wordplay.
'running' indicates an anagram (the letters run around to different places).
'near' with letters rearranged gives 'aren'.
'aren'+'a'='ARENA'
(Other definitions for arena that I've seen before include "Area of endeavour" , "where there's competition" , "Scene of action" , "Where gladiators fought" , "Sphere of intense activity" .)