Mattress holders (4)
I believe the answer is:
beds
'mattress holders' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for beds that I've seen before include "Places to sow or to sleep" , "Dormitory items" , "County; furniture" , "Cots, bunks etc -- eastern English county (abbr)" , "Shortened county" .)