Presumably star in ballet and opera? (10,4)
I believe the answer is:
performing arts
'ballet and opera?' is the definition.
I can't tell whether this defines the answer.
'presumably star in' is the wordplay.
I cannot quite see how this works, but
an anagram of 'star' is 'arts' which is located in the answer.
'in' is within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for performing arts that I've seen before include "field of activity?" , "the field of dancers and musicians" , "Stage and screen" , "Music and drama" , "stage shows, say" .)