Old American journalist (4)
I believe the answer is:
used
'old' is the definition.
(as in used or second-hand items)
'american journalist' is the wordplay.
'american' becomes 'us' (abbreviation for United States).
'journalist' becomes 'ed' (short for editor).
'us'+'ed'='USED'
(Other definitions for used that I've seen before include "Sued, having been employed" , "worked unfairly" , "Was treating" , "was milking" , "Prepossessed, perhaps" .)