Tapering pillar (7)
I believe the answer is:
obelisk
'tapering pillar' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for obelisk that I've seen before include "Square stone column that tapers" , "Pyramidal monument" , "Cleopatra's Needle, for instance" , "Tapering monumental pillar" , "Tall tapering pillar as monument or landmark" .)