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