American editor employed (4)
I believe the answer is:
used
'employed' is the definition.
('use' can be a synonym of 'employ')
'american editor' is the wordplay.
'american' becomes 'US' (abbreviation for United States).
'editor' becomes 'ed' (abbreviation).
'us'+'ed'='USED'
(Other definitions for used that I've seen before include "Old" , "Not fresh" , "Accustomed, having been put into service" , "given employment" , "exhausted" .)