One who prays to Vishnu (5)
I believe the answer is:
hindu
'one who prays to vishnu' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for hindu that I've seen before include "Adherent of an Asian religion" , "Person with faith" , "Believer in South Asian religion" , "Adherent of an eastern religion" , "Follower of India's main religion" .)