Alchemist's offering (6)
I believe the answer is:
elixir
'alchemist's offering' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for elixir that I've seen before include "Drink once supposed to prolong life indefinitely" , "Powerful potion" , "Magic cure-all" , "Alchemist's liquid" , "Magic drink believed to cure all ills" .)