Possible Clues:

• Agitation to deprive state of leader is part of the process brewing in The Beer Cellar
• It involves organic things becoming simpler things
• Agitate for empire to get rid of leader - if that happens we'll have a drink
• Head off to Italy, for one, after fizz with a couple making Champagne
• Yeast action
• Uproar at Number 10 for new leader in the process of doing something for those on the beer
• It's central to eminent art of brewing
• Process involving yeast