Burden of working with America (4)
I believe the answer is:
onus
'burden' is the definition.
('onus' can be a synonym of 'burden')
'working with america' is the wordplay.
'working' becomes 'on'.
'with' is a charade indicator (letters next to each other).
'america' becomes 'us' (abbreviation for the United States).
'on'+'us'='ONUS'
'of' is the link.
(Other definitions for onus that I've seen before include "'Burden, load (4)'" , "albatross?" , "'Burden, of proof (4)'" , "Liability" , "Duty or responsibility" .)