Possible Clues:

• Bartender, one who draws alcoholic drinks
• Old barman served plonk originally in wine cup
• Bartender once worked up about quarrel round front of tavern
• Tavern keeper
• Barman maybe offering sample outside front of pub
• One sampling drink outside front of pub — supplied by me once?
• Bartender: one sampling wine, for example, round front of pub
• Employee in pub originally included in sample
• Come to point about pious character's drinks dispenser
• Drunkenly set trap for the barman