Former "SNL" cast member, e.g (4)
I believe the answer is:
alum
(Other definitions for alum that I've seen before include "double sulphate" , "Sulphate used in dyeing and tanning" , "Aluminium/potassium sulphate" , "White mineral salt used in medicine and in dyeing" , "Colourless compound used in dyeing and tanning" .)