Upset about revolution (8)
I believe the answer is:
overturn
'upset' is the definition.
(I know that upset can be written as overturn)
'about revolution' is the wordplay.
'about' becomes 'over' (both can mean around).
'revolution' becomes 'turn' (revolution can mean a turn or rotation).
'over'+'turn'='OVERTURN'
(Other definitions for overturn that I've seen before include "Revoke" , "Invert" , "Empty out" , "Reverse (legal ruling)" , "Upset; abolish" .)