Venues constructed in stone with return of opera (6)
I believe the answer is:
stadia
'venues' is the definition.
(I have seen 'major venues' mean 'stadia' so perhaps 'venues' could also mean 'stadia')
'stone with return of opera' is the wordplay.
'stone' becomes 'st' (abbreviation).
'with' says to put letters next to each other.
'return of' is a reversal indicator.
'opera' becomes 'aida' (Verdi opera).
'aida' in reverse letter order is 'adia'.
'st'+'adia'='STADIA'
'constructed in' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for stadia that I've seen before include "large arenas" , "Bowls" , "Athletics grounds" , "Sports grounds" , "Big venues" .)