Friend in the US, one not yet out (3)
I believe the answer is:
bud
This clue is a double definition.
'friend in the us' is the first definition.
(primarily US term for a friend)
'one not yet out' is the second definition.
(part of a plant not yet out)
(Other definitions for bud that I've seen before include "Undeveloped flower" , "mate in America" , "Unopened flower" , "China to America?" , "Friend" .)