Related Clues:

• Voter, e.g.
• One old enough to know better
• Former minor
• Full price payer
• Chaperone, usually
• Film category
• Sufficiently old
• Unseen character in 'Peanuts,' generally
• Like some diapers
• Mature enough
• Legally responsible
• What "X" may mean
• Like 58-Across
• Legal, so to speak
• Fully grown