A centre back eats divine sage (6)
I believe the answer is:
buddha
'sage' is the definition.
(buddha can mean a sage or wise person)
'a centre back eats divine' is the wordplay.
'centre' becomes 'hub' (hub is a kind of centre).
'back' says the letters should be written in reverse.
'eats' means one lot of letters goes inside another.
'divine' becomes 'dd' (divine can mean theologian eg Doctor of Divinity).
'a'+'hub'='ahub'
'ahub' back-to-front is 'buha'.
'buha' enclosing 'dd' is 'BUDDHA'.
(Other definitions for buddha that I've seen before include "Philosopher who achieved enlightenment through meditation" , "Title of Gautama, Indian philosopher of 5th century BC" , "Religious leader" , "Religious figure who gained full enlightenment" , "religious picture" .)