Drug taker (4)
I believe the answer is:
user
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">drug taker</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 user that I've seen before include "Right long-established" , "One who exploits, to be sure" , "Exploiter (of others)" , "Drug-taker" , "one has to employ" .)