Publican's skill in heavy drinking (9)
I believe the answer is:
bartender
'publican's' is the definition.
(thesaurus)
'skill in heavy drinking' is the wordplay.
'skill' becomes 'art' (both can mean a talent).
'in' means one lot of letters goes inside another.
'heavy drinking' becomes 'bender' (I can't justify this - if you can you should give a lot more credence to this answer).
'art' going within 'bender' is 'BARTENDER'.
Can you help me to learn more?
(Other definitions for bartender that I've seen before include "Liquor salesman" , "Pub employee" , "American serving drinks" , "server of drinks?" , "source of 9 [ROUND] ?" .)