Possible Clues:

• Opening of musical first to last with cry of approval
• Where animals come to breathe through ice
• Helmet feature
• Opening in ice where creatures rise to breathe
• Opening in an animal carrier
• Hamster ball feature
• Vent anger at first, one part full of hate, initially
• Leeds runner needing short short break stopping for breather?
• First-class part needed to cover hospital vent
• Opening for ventilation