"Upper" or "lower" bed (4)
I believe the answer is:
bunk
'upper or lower bed' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bunk that I've seen before include "A tiered bed" , "Narrow bed; nonsense" , "Bed - garbage" , "Type of bed" , "History, according to Ford" .)