Stick up letters in position (4)
I believe the answer is:
post
I believe this is a triple definition!
'stick up' is the first definition.
(as in posting a notice in public)
'letters' is the second definition.
(letters in the mail or post)
'in' is a link.
'position' is the third definition.
(post is a kind of position)
(Other definitions for post that I've seen before include "employment" , "Member < to comment on website" , "Put a letter in the box - stop it" , "Appointment (with the Royal Mail?)" , "Publish' mail' job" .)