Definition of "cley"

"But that more heavy Birds are otherwise provided for defence, namely either by Spurs that grow on their Legs, or by the strength and sharpness of some single cley in their Foot; as I have observed in the Cassoware or Emeu"

1662, Henry More, An Antidote Against Atheism, Book II, A Collection of Several Philosophical Writings of Dr. Henry More, p. 74