Possible Clues:

• Cause of much intolerance?
• Drop enthralling pretence — some can't tolerate it
• Fail to detain one caught giving sweetener
• Be like Lear's Pobble, say, sweet thing
• The sugar in milk
• Constituent of milk
• Put work in to get beating sugar
• Type of sugar in cola set to change
• 'Nothing so milky on foot, by the sound of it (7)'
• What some folks can't tolerate