There's call for it when the show's over (7)
I believe the answer is:
curtain
'over' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for curtain that I've seen before include "Final instruction of play" , "Window drape" , "Stage concealer" , "Hanging cloth" , "Hanging fabric" .)