My bad theatre job, enormous curtains (4)
I believe the answer is:
oops
'my bad' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for oops that I've seen before include "Exclamation of making a blunder" , "Exclamation on making minor error" , "I'm sorry" , "Exclamation recognising a mistake has been made" , "My bad" .)