American newspaper boss is exploited (4)
I believe the answer is:
used
'is exploited' is the definition.
(synonyms)
'american newspaper boss' is the wordplay.
'american' becomes 'US' (abbreviation for United States).
'newspaper boss' becomes 'ed' (short for editor).
'us'+'ed'='USED'
(Other definitions for used that I've seen before include "Second-hand; exploited" , "Went through" , "Hand-me-down" , "Not fresh" , "Sued, having been employed" .)