Fireproof screen in a theatre (6,7)
I believe the answer is:
safety curtain
'fireproof screen in a theatre' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for safety curtain that I've seen before include "Fireproof screen in theatres" , "Fireproof device at the front of a theatre stage" , "Theatre fire retardant" , "fire security there!" , "Hanging item to protect a theatre audience" .)