Writing about cathedral beginning to tempt convert (9)
I believe the answer is:
proselyte
'convert' is the definition.
(term for a religious convert)
'writing about cathedral beginning to tempt' is the wordplay.
'writing' becomes 'prose' (I've seen this in another clue).
'about' is an insertion indicator.
'cathedral' becomes 'ely' (cathedral city in Cambridgeshire).
'beginning to' suggests taking the first letters.
The first letter of 'tempt' is 't'.
'ely'+'t'='elyt'
'prose' going around 'elyt' is 'PROSELYTE'.
(Other definitions for proselyte that I've seen before include "Religious convert" , "One now thinks differently" , "Convert to a religion, particularly Jewish" , "recruit" .)