Thin mattress leads to night of terrible upheaval for back (5)
I believe the answer is:
futon
'thin mattress' is the definition.
(type of mattress)
'leads to night of terrible upheaval for back' is the wordplay.
'leads to' indicates taking the first letters.
'back' says the letters should be written in reverse.
The first letters of 'night of terrible upheaval for' is 'notuf'.
'notuf' backwards is 'FUTON'.
(Other definitions for futon that I've seen before include "Japanese mattress with frame, a bed-couch" , "A Japanese folding bed-chair" , "'Japanese mattress, can be folded (5)'" , "Mattress used as a bed or sofa" , "Japanese-style mattress" .)