Possible Clues:

• Tiny amount; a church Sunday
• Least significant part of Christian festival
• How too like an owl, by the sound of it! Just a little
• Pentecost (abbrev.)
• Tiniest conceivable amount
• Wilde admits Planck's constant is a very small amount
• Little humour, it's said
• Scrap religious festival
• Tiny particle that's not quite like snow?
• Fragment created by poet when staff left