handrail (8)
I believe the answer is:
banister
'handrail' is the definition.
(I know that handrail can be written as banister)
This is all the clue.
(Other definitions for banister that I've seen before include "Staircase railing" , "Staircase handrail" , "Stair handrail and supports" , "Stair-rail" , "Support running alongside stairs" .)