The last word in devotion? (4)

I believe the answer is:

amen

I'm a little stuck... Click here to teach me more about this clue!

'the last word' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for amen that I've seen before include "Religiously 11 [THE LASTWORD]" , "Extremist" , "Name for prayer's end" , "Response to prayer" , "Churchgoer's assent?" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app