Time for a magic formula (5)
I believe the answer is:
spell
I believe this clue is a double definition.
'time' is the first definition.
(I've seen this before)
'a magic formula' is the second definition.
(I've seen this before)
'for' is the link.
(Other definitions for spell that I've seen before include "Period; piece of magic" , "Fascination" , "Magic incantation" , "Incantation; write in letters" , "get letters in order" .)