Possible Clues:

• Shakespeare's a bit of an ass perhaps, giving Nick this lowest part
• Mechanical seat
• Ass perhaps, Shakespearean character
• A total — or partial — ass?
• Recall slogan: 'British for Staying Power!'
• Black article scraped off back of sofa bed
• Base player playing lover of 16 down 11 in dream
• *Fanny
• Mechanical base
• Saying book must be taken up for bed