Column penned by perhaps bitter advocate (7)
I believe the answer is:
apostle
'advocate' is the definition.
(the apostles were advocates of Jesus)
'column penned by perhaps bitter' is the wordplay.
'column' becomes 'post' (both can mean an upright support).
'penned by' indicates putting letters inside.
'perhaps bitter' becomes 'ale' (type of beer).
'post' inserted into 'ale' is 'APOSTLE'.
(Other definitions for apostle that I've seen before include "Divine messenger" , "who can handle a spoon?" , "Early Christian teacher" , "Follower of Christ" , "Holy person" .)