Possible Clues:

• Very rare occurrence
• Song title words before "You saw me standing alone"
• If something happens once in it, it's not very often
• Blessing covering misguided mule is a rare occurrence
• Brewer known for its Belgian White ale
• The Marcels' biggest hit
• Once in this, by no means of ten
• X certificate show one's behind is rare event
• Belgian White beer brewer
• Once in a lifetime phenomenon?