Employed American journalist (4)
I believe the answer is:
'employed' is the definition.
('use' can be a synonym of 'employ')
'american journalist' is the wordplay.
'american' becomes 'US' (United States).
'journalist' becomes 'ed' (short for editor).
(Other definitions for used that I've seen before include "Prepossessed, perhaps" , "Utilised" , "Scottish expert" , "No longer new" , "Enjoyed" .)