Railing (10)
I believe the answer is:
balustrade
'railing' is the definition.
(balustrade is a kind of railing)
This is the entire clue.
(Other definitions for balustrade that I've seen before include "Railing at the side of a balcony" , "Form of railing" , "Row of short pillars with coping" , "feature of terrace, perhaps" , "Stair rail and its supports" .)