As if by magic (3,6)
I believe the answer is:
hey presto
'as if by magic' is the definition.
(magic words)
This is the entire clue.
(Other definitions for hey presto that I've seen before include "Conjuror's command or exclamation" , "Conjuror's exclamation at the climax of a trick" , "revealing remark?" , "that's the trick" , "suddenly, as if by magic" .)