Homecoming guest (4)
I believe the answer is:
alum
'homecoming guest' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alum that I've seen before include "White mineral salt used in medicine and in dyeing" , "Compound used in dyeing and to stop bleeding" , "Colourless compound used in dyeing and tanning" , "double sulphate" , "Compound used in tanning and dying" .)