App customer (4)
I believe the answer is:
user
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">app customer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for user that I've seen before include "Exploiter (of others)" , "Operator; drug addict" , "Druggie" , "Maybe one needing pot" , "One operating something" .)