Stairway post (5)
I believe the answer is:
newel
'stairway post' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for newel that I've seen before include "Top/bottom supporting post of a stair-rail" , "Column" , "Post supporting stair rail" , "Central pillar of a spiral staircase" , "Main post supporting handrail on stairs" .)