Possible Clues:

• Doc for snorers
• Suffix with ''differ'' or ''insist''
• Creature in 'The Two Towers'
• Doc seen for head colds
• Doc who might diagnose a deviated septum
• Exist extension
• Doc for head colds: abbr.
• Ending with insist
• 'Say 'ah'' doc
• Sinus specialist: Abbr.