Entertained, in the morning, American editor (6)
I believe the answer is:
amused
'entertained' is the definition.
(amusing is a kind of entertaining)
'morning american editor' is the wordplay.
'morning' becomes 'am'.
'american' becomes 'us' (abbreviation for United States).
'editor' becomes 'ed' (abbreviation).
'am'+'us'+'ed'='AMUSED'
'in the' is the link.
(Other definitions for amused that I've seen before include "Pleasantly occupied" , "Provoked mirth in" , "was entertaining" , "Kept someone entertained" , "happily occupied" .)