Go away and live with American bird (4,2)
I believe the answer is:
beat it
'go away' is the definition.
(I've seen this before)
'live with american bird' is the wordplay.
'live' becomes 'be' (synonyms).
'with american' becomes 'a' (common abbreviation - e.g. in organisation names. I am not sure about the 'with' bit.).
'bird' becomes 'tit' (tit is a kind of bird).
'be'+'a'+'tit'='BEAT IT'
'and' acts as a link.
(Other definitions for beat it that I've seen before include "make off furtively" , "Scarper" , "leave" , "Scram, get lost" , "try out drum kit?" .)