Possible Clues:

• Dentist's task
• Big job for a driller
• Passage through which nerve and blood vessels enter pulp cavity of tooth
• Redhead is too upset going around Venice? The bridge-worker has a view on this!
• Dental passage
• Tooth-saving procedure
• Drawn-out dental procedure
• One of the underground systems has a chamber for mouthy type facing the drill perhaps
• Almost alone, actor struggles to get canine part?
• Ordeal at the dentist's office