One can't fly through the multiverse (3)
I believe the answer is:
emu
'one can't fly' is the definition.
(emus are flightless birds)
'through the multiverse' is the wordplay.
'through' says the answer is hidden in the clue.
'EMU' can be found hidden inside 'the multiverse'.
(Other definitions for emu that I've seen before include "Hull's character" , "Australian bird related to the ostrich" , "that doesn't get off the ground" , "Ostrich-like bird" , "Extinct bird" .)