"You said it, brother!"
I believe the answer is:
amen
'you said it brother' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for amen that I've seen before include "Name for end to prayer" , "Prayerful last word" , "statement of affirmation" , "as agreed!" , "Churchgoer's assent?" .)