On which to write letters home? (3)
I believe the answer is:
pad
I believe this is a double definition.
'on which to write letters' is the first definition.
(letters can be written on a pad of paper)
'home?' is the second definition.
(pad can mean a person's home)
(Other definitions for pad that I've seen before include "eg Bedsitter" , "Walk softly on flat or bedsit" , "protection for member" , "Piece of soft material or bachelor's flat" , "Stuff the animal's foot" .)