Title character of a Blatty novel (8)
I believe the answer is:
exorcist
'title character of a blatty novel' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for exorcist that I've seen before include "He drives the devil out by prayer" , "He'll remove it" , "One who drives out evil spirits by prayer" , "One who supposedly drives out evil spirits" , "One who expels evil spirits" .)