What some smartphones run on (3)
I believe the answer is:
ios
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">what some smartphones run on</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 ios that I've seen before include "Apple's mobile system, in short" , "Another Greek island" , "Greek island and mobile phone system" , "place?" , "Greek isle" .)