Balustrade (7)
(Other definitions for parapet that I've seen before include "Low wall round edge of balcony" , "Low wall along the edge of a balcony" , "Fortification consisting of a low wall" , "Wall's top" , "Breastwork" .)
'balustrade' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for railing that I've seen before include "Mocking" , "Type of fence - scoffing" , "Protesting (about); fence" , "Metal barrier" , "Barrier of a horizontal bar and supports" .)