Outline leaders of cast engaging numbers in dress circle (8)
I believe the answer is:
scenario
'outline' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for scenario that I've seen before include "expected sequence of events" , "Imagined sequence" , "Dramatic set-up" , "Film/novel plot outline" , "In plot of movie, for instance" .)