Peaceful American gets release from duties (7)
I believe the answer is:
quietus
'release from duties' is the definition.
(quietus can mean death or demise)
'peaceful american' is the wordplay.
'peaceful' becomes 'quiet' (associated in meaning).
'american' becomes 'us' (abbreviation for United States).
'quiet'+'us'='QUIETUS'
'gets' acts as a link.
(Other definitions for quietus that I've seen before include "discharge" , "Final riddance - not quite quite us" , "Extinction, death" , "passing away" , "Curtains" .)