Word at the end of a prayer (4)
I believe the answer is:
amen
'word at the end of a prayer' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for amen that I've seen before include "Religiously 11 [THE LASTWORD]" , "Word of approval" , "as agreed!" , "Conclusion of prayer" , "Name for end to prayer" .)