Fanatical devotee (6)
I believe the answer is:
addict
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fanatical devotee</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for addict that I've seen before include "One hooked on drugs" , "One hooked on something" , "Regular drug user" , "Slave to a chemical substance" , "One dependent on drugs" .)