In most cases, Maria had everything (6)
I believe the answer is:
callas
'in most cases' is the definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
'maria had everything' is the wordplay.
I cannot really see how this works, but
'everything' could be 'all' (all things) and 'all' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for callas that I've seen before include "Noted late soprano of Greek background" , "Greek diva" , "Arguably, the greatest diva of them all" , "Superb soprano of Greek background" , "Maria, Greco-American soprano" .)