Publican's target includes castle (9)
I believe the answer is:
innkeeper
'publican's' is the definition.
(a publican runs a pub)
'target includes castle' is the wordplay.
'target' becomes 'inner' (I've seen this before).
'includes' indicates putting letters inside.
'castle' becomes 'keep' (I've seen this in other clues).
'inner' placed around 'keep' is 'INNKEEPER'.
(Other definitions for innkeeper that I've seen before include "Tavern owner" , "Pub landlord" , "For example, Mistress Quickly" , "local manager" , "Accommodating type" .)