Ritual of expelling evil spirits (8)
I believe the answer is:
exorcism
'ritual of expelling evil spirits' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for exorcism that I've seen before include "Ritual of driving out evil spirit" , "Ritual to banish evil spirits" , "Ritual of expelling evil spirits" , "Dispossession" , "Ceremony to release evil spirits" .)