Related Clues:

• Kind of particle or wave
• Reaction to a surprise ending, perhaps
• Sudden intake of air
• Gaps in struggle for breath
• The first Greek letter
• Short sharp intake of breath
• Struggle for breath with open mouth
• Puff, struggle for breath
• Inhale sharply with astonishment
• First letter of the Greek alphabet
• Short laboured intake of breath
• Hal comes first with his Pa
• One might bet a follower of this first
• Pa, that's the first letter from Hal
• Around the South it's open to have a breather