A half-hearted mob at theatre, possible to reform (9)
I believe the answer is:
reparable
'possible to reform' is the definition.
I can't tell whether this definition defines the answer.
'a half-hearted mob at theatre' is the wordplay.
'a half-hearted mob' becomes 'arable' (I can't justify this - if you can you should give a lot more credence to this answer).
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'theatre' becomes 'rep' (repertory theatre).
'arable' after 'rep' is 'REPARABLE'.
Can you help me to learn more?
(Other definitions for reparable that I've seen before include "Able to be fixed" , "Able to be rectified" .)