Tory scum mad about anarchist leader as usual (9)
I believe the answer is:
customary
'as usual' is the definition.
(I've seen this before)
'tory scum mad about anarchist leader' is the wordplay.
'mad' indicates an anagram.
'about' means one lot of letters goes inside another.
'leader' says to take the initial letters.
The initial letter of 'anarchist' is 'a'.
'tory'+'scum'='toryscum'
'toryscum' with letters rearranged gives 'customry'.
'customry' going around 'a' is 'CUSTOMARY'.
(Other definitions for customary that I've seen before include "precedent" , "Commonly used or practised" , "Courts may find this usual" , "Conventional" , "Normal, usual" .)