Cushion for flat (3)
I believe the answer is:
pad
I believe this is a double definition.
'cushion' is the first definition.
(thesaurus)
'flat' is the second definition.
(person's home)
'for' acts as a link.
(Other definitions for pad that I've seen before include "pack" , "Sheets of paper fastened together along one edge" , "Tread softly" , "Residence" , "Fill with extra material in order to lengthen" .)