Related Clues:

• Talk idly
• Energy source
• Chemist's study
• Driver's need
• Stove option
• Burn it by stepping on it
• Windbag's output
• Balloon contents
• Petrol
• Filling-station supply
• Bombas-tic talk
• 21-Across, for one
• Atmosphere makeup
• Station ration
• Nitrogen, for instance