Writer possibly in love with saint (8)
I believe the answer is:
novelist
'writer' is the definition.
(I know that novelist is a type of writer)
'possibly in love with saint' is the wordplay.
'possibly' indicates an anagram.
'with' is a charade indicator (letters next to each other).
'saint' becomes 'st' (abbreviation).
'in'+'love'='inlove'
'inlove' anagrammed gives 'noveli'.
'noveli'+'st'='NOVELIST'
(Other definitions for novelist that I've seen before include "King maybe" , "Writer of long stories" , "I've written" , "Book writer" , "Eliot or Bronte" .)