Poster showing a shopkeeper (9)
I believe the answer is:
stationer
This clue is a double definition.
'poster' is the first definition.
(I've seen this before)
'a shopkeeper' is the second definition.
(I've seen this before)
'showing' is the link.
(Other definitions for stationer that I've seen before include "Poster" , "has what writer needs" , "Writing-materials shop" , "Dealer in writing materials" , "Tradesman" .)