Possible Clues:

• Agitatedly tuts about doctor, being extreme
• (To the) maximum extent
• Do your best to be grand in such a stout way (6)
• Maximum possible
• The greatest stout brewing involves malt primarily
• The furthest point or degree
• In the wings, upset mezzo soloist can be extreme
• Greatest - extreme
• Greatest; most extreme
• Work out sum and tot maximum