Ultimately wanting Apple to supply computer (6)
I believe the answer is:
laptop
'computer' is the definition.
(laptop is a part of computer)
'ultimately wanting apple to supply' is the wordplay.
'ultimately wanting' means to remove the last letter (wanting can mean lacking).
'supply' indicates an anagram (in a supple way).
'apple' with its last letter taken off is 'appl'.
'appl'+'to'='applto'
'applto' anagrammed gives 'LAPTOP'.
(Other definitions for laptop that I've seen before include "Portable computer" , "Kind of computer" , "Small computer" , "device?" , "Aid for businessman" .)