Possible Clues:

• Prince Andy's ex
• Prince Andrew's ex
• Princess Beatrice's mom
• Sobriquet shared by a duchess and an ex-football manager
• "Big Girls Don't Cry" singer
• Vocalist for the Black Eyed Peas
• Manchester United manager familiarly
• Black Eyed Peas singer
• One of the writers of 'Boom Boom Pow'
• A Black Eyed Pea