Crossword puzzle clue "almost impossible as a task"

Almost impossible, as a task

___ window (impossible task)

Photographer's impossible task?

Impossible task, so to speak

Elaborate practical joke where the victim is left in the dark charged with an impossible task

"It's almost impossible to know ..."

Situation from which it is almost impossible to proceed

"A literary device for saying almost everything about almost anything": Huxley