It's not well done in extra rehearsals (4)
I believe the answer is:
rare
'it's not well done' is the definition.
(as in a steak)
'in extra rehearsals' is the wordplay.
'in' says the answer is hidden in the clue.
'RARE' can be found hidden inside 'extra rehearsals'.
(Other definitions for rare that I've seen before include "Special" , "Ben Jonson was considered so" , "Rear up, being scarce" , "not often spotted" , "not dense" .)