Possible Clues:

• A prison-camp child that is growing up!
• A certain point underground?
• At last! Gem I misplaced found on floor of cave
• What may form on cave floor
• A prison camp child growing up
• One growing up as prison child
• Cave formation from dripping water, usually with a rounded tip
• Trifling sum prison camp put on deposit
• Cave floor growth
• Get atlas out crossing motorway, seeing pillar pointing up