American friend’s name rejected (3)
I believe the answer is:
bud
'american friend's' is the definition.
(US term for friend)
'name rejected' is the wordplay.
'name' becomes 'dub' (as in dubbing someone with a particular name).
'rejected' says the letters should be written in reverse.
'dub' reversed gives 'BUD'.
(Other definitions for bud that I've seen before include "Unopened flower" , "It will eventually become a leaf or flower" , "American beer" , "Flower yet to open" , "Shoot, sprout" .)