End of a prayer (4)
I believe the answer is:
amen
'end of a prayer' 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 "statement of affirmation" , "prayer's ending" , "Extremist" , "Prayerful last word" , "Name for prayer's end" .)