Word repeated in Hozier's "Take Me to Church" (4)
I believe the answer is:
amen
'word repeated in hozier's take me to church' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for amen that I've seen before include "Last word of prayer" , "Word at the end of a prayer" , "I agree!" , "Word of approval" , "Extremist" .)