Possible Clues:

• The capital
• Salon do, not including a 6
• L and D both get on capitally together
• American writer's novel on old and new
• My challenge on Sunday, thraldom, on an' on, painfully!
• English city in "Paddington"
• — Plane; — pride
• Liberal Spanish gent added to working capital
• Where Martin 21 found his murderee?
• See northern fellow in the metropolis