Grand circular stadium (6)
I believe the answer is:
ground
'stadium' is the definition.
(I've seen this before)
'grand circular' is the wordplay.
'grand' becomes 'G' (synonyms).
'circular' becomes 'round' (synonyms).
'g'+'round'='GROUND'
(Other definitions for ground that I've seen before include "turned to dust" , "Worked hard" , "Powdered; land" , "cause" , "foundation course?" .)