Sorcery makes five ducks go to five hundred ducks (6)
I believe the answer is:
voodoo
'sorcery' is the definition.
(thesaurus)
'five ducks go to five hundred ducks' is the wordplay.
'five' becomes 'v' (roman numeral).
'ducks' becomes 'oo' (I've seen this in other clues).
'go to' is a charade indicator (letters next to each other).
'five hundred' becomes 'd' ('D' can be a synonym of 'five hundred').
'ducks' becomes 'oo' (I've seen this in other clues).
'v'+'oo'+'d'+'oo'='VOODOO'
'makes' is the link.
(Other definitions for voodoo that I've seen before include "Caribbean cult involving witchcraft" , "Type of witchcraft" , "Caribbean magic cult" , "In the air" , "West Indian witchcraft" .)