Possible Clues:

• "See you next fall!" elicitor
• Pratfall
• See 63-Across
• React to acid
• Business undertaking
• Ride for a fall?
• Fall/stand -- see 14 (4)
• Flight that may be round
• "Round" thing suggested by the first words of 17-, 26-, 46- and 61-Across
• Err; journey