Choice of potion, brew? (6)
I believe the answer is:
option
'choice' is the definition.
(I know that choice can be written as option)
'potion brew?' is the wordplay.
'brew?' is an anagram indicator (I've seen 'brew' mean this).
'potion' with letters rearranged gives 'OPTION'.
'of' acts as a link.
(Other definitions for option that I've seen before include "Right to choose" , "Freedom to choose" , "Choice of portion" , "An act of choosing" , "Altenative choice" .)