Revolutionary (7)
'revolutionary' is the definition.
(radical can mean revolutionary or extreme)
This is the entire clue.
(Other definitions for radical that I've seen before include "Primitive" , "Innovative, progressive" , "Drastic or thorough as changes may be" , "Deep" , "Thoroughgoing - (popularly) extremist" .)
'revolutionary' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for firebrand that I've seen before include "Agitator" , "One who stirs up trouble" , "Energetic person often fomenting trouble" , "Rabble-rouser" , "Troublemaker" .)