Anger about a politician causes riot (7)
I believe the answer is:
rampage
'riot' is the definition.
(I've seen this before)
'anger about a politician' is the wordplay.
'anger' becomes 'rage' (rage is a kind of anger).
'about' indicates putting letters inside.
'politician' becomes 'mp' (Member of Parliament).
'a'+'mp'='amp'
'rage' placed around 'amp' is 'RAMPAGE'.
'causes' is the link.
(Other definitions for rampage that I've seen before include "Run wild" , "A mad rush" , "Charge around being wild and destructive" , "Rage wildly around" , "Violent rush" .)