Staircase banister (4)
(Other definitions for rail that I've seen before include "Bar - marsh bird" , "Part of train track" , "Bar for hanging; bird as corncrake" , "Complain intemperately" , "wader" .)
(Other definitions for railing that I've seen before include "Type of fence - scoffing" , "Fence of metal bars" , "Fulminating against the barrier?" , "Complaining bitterly - barrier" , "Iron barrier" .)