Am leaving US to find evergreen shrub (5)
I believe the answer is:
erica
'evergreen shrub' is the definition.
(I've seen this in another clue)
'am leaving us' is the wordplay.
'leaving' indicates named letters should be taken away.
'us' becomes 'America' (synonyms).
'america' with 'am' taken away is 'ERICA'.
'to find' is the link.
(Other definitions for erica that I've seen before include "found on the moors" , "hardy shrub" , "Girl's name - I care (anag)" , "Woman" , "Shrub genus; girl's name" .)