Magical or medicinal potion (6)
I believe the answer is:
elixir
'magical or medicinal potion' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for elixir that I've seen before include "wonder drug" , "Potion, panacea" , "Miraculous cure" , "Quintessence" , "Philosopher's stone" .)