Alexander ingredient (3)
I believe the answer is:
'alexander ingredient' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gin that I've seen before include "Spirit; cotton machine" , "Animal trap or alcoholic drink" , "Alcoholic drink once called mother's ruin" , "Trap; mother's ruin" , "Clear alcoholic drink" .)