Do remedial work in the theatre (7)
I believe the answer is:
operate
'do remedial' is the definition.
I can't tell whether this defines the answer.
'work in the theatre' is the wordplay.
'work' becomes 'opera' (musical work).
'in the theatre' becomes 'te' (I can't justify this - if you can you should give a lot more credence to this answer).
'opera'+'te'='OPERATE'
Can you help me to learn more?
(Other definitions for operate that I've seen before include "Carry out surgery" , "Perform surgery or run a machine" , "Function; run" , "Cause to function" , "Make to work" .)