Possible Clues:

• Active principle of intoxicating drinks
• That whose strength is measured by proof
• Drink everyone's taken when consuming salmon
• Still stuff
• That's enough to make Hal cool and tight
• It can make one merry - and solvent
• Henry's coming in unflustered after a litre - lager, perhaps
• An intoxicant
• Ethanol
• Tipsy school-leaver veers off for more drink, possibly