One on a computer (4)
I believe the answer is:
user
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">one on a computer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for user that I've seen before include "Someone who exploits another" , "One who works an appliance" , "Utiliser" , "Person employing something" , "Operator (of something)" .)