Violent protesters initially roaring 'Tories out' (7)
I believe the answer is:
rioters
'violent protesters' is the definition.
(I've seen this before)
'initially roaring tories out' is the wordplay.
'initially' suggests taking the first letters.
'out' indicates an anagram (out can mean wrong or inaccurate).
The first letter of 'roaring' is 'r'.
'tories' with letters rearranged gives 'ioters'.
'r'+'ioters'='RIOTERS'
(Other definitions for rioters that I've seen before include "Crowd disturbing the peace" , "Demonstrators" , "Rabble-rousers" , "Violent protesters" , "They disturb the peace" .)