Fanatic — monster (5)
I believe the answer is:
fiend
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">fanatic</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I know that fanatic can be written as fiend)</span><br/ ><br/ >'<span class="explanation-format__original">monster</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that monster can be written as fiend)</span><br/ ><br/ ></span>
(Other definitions for fiend that I've seen before include "Demon, ogre" , "addict" , "Evil supernatural being" , "Demon; cruel person" , "Evil spirit, demon" .)