Backless seat (5)
'backless seat' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for stool that I've seen before include "item of furniture here" , "Seat without a back" , "Armless seat" , "Three-legged backless seat" , "Motion" .)
(Other definitions for divan that I've seen before include "Couch - bed" , "Sideless, backless couch" , "resting place" , "Viand (anag.)" , "Sort of bed" .)