Possible Clues:

• Bring-a-bottle party? Impossible
• 'Impossible for me!'
• 'Sorry, Charlie!'
• 'Out of my capabilities'
• Absolutely not!
• "Above my pay grade" ... and, read in four parts, a hint to 16-, 24-, 32-, 40- and 49-Across
• 'Above my pay grade' ... and, read in four parts, a hint to 16-, 24-, 32-, 40- and 49-Across
• Informal refusal
• I am unable to get even mains in new condo
• Out of the question