Dropped 3 Strike on pitch in dirt

[U of M Sam]

Originally posted by Mista Bone
This has come up several times and I can't find reference in the books:

Strike three swung on a pitch in the dirt. Catcher catches it "clean" on a hop. I've always interpreted this to be a catch and not a dropped third strike, under the simple premise that the catcher did not drop the ball but caught it on the original delivery.

Thoughts....?

This is not a catch. How can it be a "clean" catch on a hop? Please check rule book definition of "catch".