Rising public disorder bill in America a shambles (8)
I believe the answer is:
abattoir
'shambles' is the definition.
('abattoir' can be a synonym of 'shambles')
'rising public disorder bill in america a' is the wordplay.
'rising' says the letters should be written backwards (going up in a down clue).
'public disorder' becomes 'riot' (I've seen this before).
'bill in america' becomes 'tab' (american english for the bill at end of meal say).
'riot'+'tab'+'a'='riottaba'
'riottaba' reversed gives 'ABATTOIR'.
(Other definitions for abattoir that I've seen before include "Damage (metal) by chemical action" , "scene of slaughter" , "It might make a killing" , "A slaughter house for cattle" , "building where blood is shed" .)