Related Clues:

• Old knockout
• Antiquated anesthetic
• A hydrocarbon depicted as planar hexagon
• Early number?
• Number three substituted
• Air, poetically
• Clear night sky, in poetry
• Number used no more?
• Highly flammable liquid once used as an anaesthetic
• Number one from one of two
• A number rule the roost, to some extent
• Solvent; clear sky
• Old number — some leave the room
• I'm volatile in that place, the first to rise up
• Hydrocarbon with ring-shaped molecules