Drug user (6)
I believe the answer is:
addict
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">drug user</span>' is the definition.<br/ ><span class="explanation-format__explanation">(addict is a kind of drug user)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for addict that I've seen before include "Junkie, dependant" , "One who is dependent on something, alcohol say" , "Fanatical devotee" , "Person with compulsive dependence on drugs" , "Bricklayer's tool" .)