Possible Clues:

• Capital letters in biro in a novel
• A leading investor to rip off in Ulster city?
• Capital of the North to expose witchcraft
• Capital for Pole, first class, with tailless bird
• Capital Spaniard raised, expending energy for nothing
• The Green City in the Sun
• A robin flying around one city
• New impression made by witchcraft in African capital
• One Irish king repelled outside old capital
• Robinia spreading in capital city