American fellows providing the final word (4)
I believe the answer is:
amen
'the final word' is the definition.
(last word in a prayer)
'american fellows' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'fellows' becomes 'men' (fellow can mean a man).
'a'+'men'='AMEN'
'providing' acts as a link.
(Other definitions for amen that I've seen before include "Approve" , "So let it be" , "Extremist" , "Prayer ending" , "Put name to end of payer" .)