Possible Clues:

• "And __ off!"
• "As you ___"
• "___ off to see the wizard . . ."
• 'Now, where ___ we?'
• ''Those __ the days!''
•     Used to be
• "What __ you thinking?"
• See 15-Across
• "While ___ on the subject . . ."
• ''As it'' or ''as you'' follower