Letters column? (4)
I believe the answer is:
post
This clue is a double definition.
'letters' is the first definition.
(thesaurus)
'column?' is the second definition.
(I have seen 'A column' mean 'post' so perhaps 'column' could also mean 'post')
(Other definitions for post that I've seen before include "Upright - letters" , "delivery" , "Prevent (cheque) being cashed immediately" , "Leave message online" , "picket" .)