Possible Clues:

• Lily is at the bottom of that call
• By the sound of it, a half-century goes off with Lily
• 'When the angry trumpet sounds ___': Shak.
• Reverse picture on wall with a warning
• The Bard's call to arms
• Shakespearean warning
• A work of art, when mounted, creates disturbance
• How Lily follows Albert for a call to arms
• There's some disturbance when it's a pound a drink
• Warning bell (archaic)