Pub worker (9)
'pub worker' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bartender that I've seen before include "One serving" , "He serves" , "source of 9 [ROUND] ?" , "Taverner" , "Liquor salesman" .)
(Other definitions for barman that I've seen before include "Who could help with getting mops and brooms" , "he might be responsible for you getting shot" , "He serves drinks" , "He works in a pub" , "Club worker" .)