Apple's mobile platform (3)
I believe the answer is:
ios
'apple's mobile platform' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ios that I've seen before include "Greek island and mobile phone system" , "Another Greek island" , "Apple's mobile system, in short" , "Greek isle" , "Greek island in the Cyclades" .)