On which performers stand out: huge stars performing with the theatre, primarily (6,5)
I believe the answer is:
thrust stage
'on which performers stand out' is the definition.
(a stage which extends out into the audience)
'huge stars performing with the theatre primarily' is the wordplay.
'performing with' indicates anagramming the letters.
'primarily' suggests taking the first letters.
The initial letters of 'the theatre' is 'tt'.
'huge'+'stars'='hugestars'
'hugestars' with its letters mixed up with 'tt' makes 'THRUST STAGE'.
(Another definition for thrust stage that I've seen is " part of theatre".)