Contribute online column (4)
I believe the answer is:
post
I believe this clue is a double definition.
'contribute online' is the first definition.
(I've seen this before)
'column' is the second definition.
(both can mean an upright support)
(Other definitions for post that I've seen before include "Maybe letters" , "ob" , "Part of address" , "picket" , "Prefix meaning after" .)