Possible Clues:

• A little light handle
• Vertical mine entrance
• Elevator enclosure
• Ore corridor
• Vertical passage of mine (quiet at the back!)
• Arrow of sunlight?
• 'Who's the cat who will creep out, when there's danger all about?'
• It may be sunk in a marsh afterwards
• Treat unfairly, in slang
• Ray of light; treat unfairly