Word of agreement (4)
'word of agreement' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for amen that I've seen before include "statement of affirmation" , "Conclusion of prayer" , "Word of agreement" , "Name for end to prayer" , "Put name to end of payer" .)
(Other definitions for true that I've seen before include "Consistent with fact" , "Right; genuine" , "Exact, factual" , "A false alternative?" , "indeed" .)
(Other definitions for yeah that I've seen before include "quite casually" , "Affirmative response (informal)" , "Surely" , "Certainly" , "Definitely (informal)" .)
(Other definitions for righto that I've seen before include "Okey doke" , "Correct" , "Okey-dokey" , "Okay!" , "very well" .)