Possible Clues:

• Difficult request: a bit of buttered roll? A toastie's offered up
• Challenge that's taxing Jesuits, say over six feet
• Preposterous sort demanding request
• Two dozen giraffes say one will be tricky to fill
• Request that's hard to fulfill
• Hard task for steeplejack?
• Time everybody on command -- that's difficult
• Very difficult assignment from diminutive monks? The opposite!
• Ben Nevis, Snowdon, Scafell Pike? That's a challenge
• High Commission that's not easily satisfied