Lines penned by directors offering post (7)
I believe the answer is:
bollard
'post' is the definition.
(I know that bollard is a type of post)
'lines penned by directors' is the wordplay.
'lines' becomes 'll' (two abbreviations for line).
'penned by' indicates putting letters inside (inserted letters are penned in).
'directors' becomes 'board' (board of directors).
'll' put within 'board' is 'BOLLARD'.
'offering' is the link.
(Other definitions for bollard that I've seen before include "Thick post for mooring" , "Mooring post - traffic restriction device" , "Strong post" , "Post on road or quay" , "Short post barring traffic" .)