Magic vehicle carrying Santa to France with bit of help (7,2,4)
'magic' is the definition.
(sleight of hand is a kind of magic)
'vehicle carrying santa to france with bit of help' is the wordplay.
'vehicle carrying santa' becomes 'sleigh' (vehicle used by Santa Claus).
'france' becomes 'f'.
'with' says to put letters next to each other.
'bit of help' becomes 'hand' (to give someone a hand is to give them help).
(Other definitions for sleight of hand that I've seen before include "Prestidigitation", "Conjuror's skill", "Legerdemain", "Manual dexterity in conjuring", "Doctor or student doctor".)