Possible Clues:

• One of two in Canada?
• Dull sound
• Vowel sound represented by an upside-down "e"
• Many a vowel
• Upside down, lower case 'e'
• One's at either end of "America"
• 'The' vowel
• Vowel sound represented by an upside-down 'e'
• One of two heard in America
• A neutral middle vowel that occurs in unstressed syllables