Poet and old priest to back (5)
I believe the answer is:
eliot
'poet' is the definition.
(TS Eliot)
'old priest to back' is the wordplay.
'old priest' becomes 'eli' (Biblical character).
'back' shows that the letters should be reversed in order.
'to' back-to-front is 'ot'.
'eli'+'ot'='ELIOT'
'and' acts as a link.
(Other definitions for eliot that I've seen before include "T.S. --, poet" , "Middlemarch author" , "Pseudonymous writer" , "Murder in the Cathedral author" , "T S . . . . ., great poet of 'The Waste Land'" .)