Operator (4)
I believe the answer is:
user
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">operator</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for user that I've seen before include "One taking drugs" , "Drug-taker" , "Drug addict (colloq.)" , "one has to employ" , "Ruse for employer" .)