Possible Clues:

• Most unfriendly streets for bird to nest in
• Most austere
• Most unforgiving
• Back set for surgery that's most serious
• Extremely tough way Irish writer leads or Hemingway follows
• Most unfriendly old author on street
• Most stony streets in which flier will settle
• Most severe saint with 'important' name
• South Terrace has refuge that's most austere
• Harshest lough surrounded by saints