Sentence:  ... an <WSD>"assart</WSD>" of the Forest, is the greatest offence or trespasse of all other, that can be done in the forest, to vert or venison, containing in it as much as waste or more. For whereas the waste of the Forest, is but the felling and cutting downe of the couerts, which may grow againe in time: an <WSD>"assart</WSD>", is a plucking them vp ... 
Meaning of the word marked with <WSD> tags:  The act or offence of grubbing up trees and bushes, and thus destroying the thickets or coverts of a forest.