Organ at the rehearsal centre (3)
I believe the answer is:
ear
'organ' is the definition.
(ear is a kind of organ)
'the rehearsal centre' is the wordplay.
'centre' indicates the central letters.
The centre of 'rehearsal' is 'EAR'.
'at' acts as a link.
(Other definitions for ear that I've seen before include "Fruiting head of corn" , "Seed container" , "Ability to recognise sounds" , "See 8" , "Listener in the cornfield" .)