Staircase post (5)
I believe the answer is:
newel
'staircase post' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for newel that I've seen before include "Main post supporting handrail on stairs" , "domestic post" , "Post that's part of a flight of stairs" , "Central pillar of a spiral staircase" , "Yucatan native" .)