Possible Clues:

• Lift stakes, then put a new fence at last
• UN, pet hate, mobilised to increase risk?
• Increase the stakes
• Put out two forms of energy, including nuclear, principally to increase risk
• Increase the risks, having climbed the volcano from the back
• Make things interesting, so to speak
• Play for higher stakes
• How one might find Etna to increase danger?
• Increase what is at stake
• Raise stakes in a game ... and a hint to a hidden feature of five Down puzzle answers