Brewer's: Clipping Pace
(A). Very fast. A clipper is a fast-sailing vessel.
“Leaving Bolus Head, we scudded on at a clipping pace, and the skiff yielded so much to the breeze that Bury said we must reef the mainsail.” —W. S. Trench: Realities of Irish Life, chap. x
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894