Extremist figure in racial disturbance (7)
I believe the answer is:
radical
'extremist' is the definition.
(I know that extremist can be written as radical)
'figure in racial disturbance' is the wordplay.
'figure' becomes 'c' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'racial disturbance' becomes 'radial' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'c' inserted inside 'radial' is 'RADICAL'.
Can you help me to learn more?
(Other definitions for radical that I've seen before include "Dial car in order to be drastic" , "Progressive; extreme" , "Deep-seated" , "Drastic or thorough as changes may be" , "Militant" .)