"clearly impossible" is a grammatically correct phrase that can be used in written English.
For example, you could say: "It was clearly impossible to finish the task in the allotted time."
Captain Eads, with his jetties, has done a work at the mouth of the Mississippi which seemed clearly impossible; so we do not feel full confidence now to prophesy against like impossibilities.
Agreement was clearly impossible.
Which is clearly impossible.
But it was clearly impossible to continue.
It is clearly impossible in the time remaining.
That would be clearly impossible for troubled borrowers.
It was clearly impossible to be in both locations.
Multisplit should be avoided unless it is clearly impossible to decently load balance using whole cells.
Resistance to his magic, even by these self-possessed and serious poetesses, is clearly impossible.
Why do we enjoy experiencing what seems clearly impossible, or at least beyond our powers of explanation?
Any change of course in European policy would require him to admit his mistakes, and that is clearly impossible.
