Column is penned by odd bloke (7)
I believe the answer is:
obelisk
'column' is the definition.
(obelisk is a kind of column)
'is penned by odd bloke' is the wordplay.
'penned by' means one lot of letters goes inside another.
'odd' indicates anagramming the letters.
'bloke' anagrammed gives 'obelk'.
'is' put inside 'obelk' is 'OBELISK'.
(Other definitions for obelisk that I've seen before include "Monument with tall pillar and tapering top" , "Square stone column that tapers" , "Tapering, rectangular stone column" , "Stone pillar tapering towards a point" , "Tapering square stone monument" .)