Related Clues:

• Castle-building material
• Director of 'JFK,' 'Nixon' and 'W.'
• Eyelid hair
• Lake skipper?
• With 42-Across, time of cavemen
• It might be batted at a knockout
• Mascara destination
• Stroke of a whip
• See 5
• See 3
• See 1
• See 19
• See 21
• See 7
• See 23