Wooden panelling was hemming in bed (8)
I believe the answer is:
wainscot
'wooden panelling' is the definition.
(I've seen this before)
'was hemming in bed' is the wordplay.
'hemming' means one lot of letters goes inside another (hem can mean to enclose).
'bed' becomes 'cot' (cot is a kind of bed).
'was' enclosing 'in' is 'wains'.
'wains'+'cot'='WAINSCOT'
(Other definitions for wainscot that I've seen before include "Wooden panelling on lower wall of a room" , "Boarding" , "I go up the wall" , "Lower part of interior wall" , "Wooden panel on a wall" .)