Manipulated American editor (4)
I believe the answer is:
used
'manipulated american editor' is the definition.
(I've seen this before)
'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 "Sued (anag.)" , "Second-hand, not new" , "with some traffic" , "took a chance on becoming dependent" , "Dog-eared" .)