One's often high during a performance but down after the show (7)
I believe the answer is:
curtain
'one's often high during a performance' is the definition.
I cannot 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 "It can be drawn" , "Cover for window etc" , "Hanging, window cover" , "Window drape" , "It's raised before the start of a play" .)