Magic formula takes some time (5)
I believe the answer is:
spell
This clue is a double definition.
'magic formula' is the first definition.
(magic spell)
'some time' is the second definition.
(both can mean a short period of time)
'takes' acts as a link.
(Other definitions for spell that I've seen before include "Deliveries" , "Words with magical power, or a period of time" , "Incantation; splinter of wood" , "Incantation; write in letters" , "Period (of work); incantation" .)