Possible Clues:

• Scales a rock wall
• Gets a promotion
• Moves upward gradually
• Goes to the top of
• Scales initially costing an arm and a leg?
• Cold legs? They could pose problems for mountaineers
• Participates in the Reek Sunday pilgrimage, say
• Ascends a hill or ladder
• 'What the centipede has, perhaps (6)'
• Ascends with difficulty