Alchemist's potion (6)
I believe the answer is:
elixir
'alchemist's potion' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for elixir that I've seen before include "Medicinal liquid believed to cure all ills" , "Magical or medicinal potion" , "Substance believed to cure all ills" , "Restorative drink" , "A life-giving drink" .)