Portion of a footwear sole

FIG. 1 is a perspective view of a portion of a footwear sole showing my new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a left side view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a front view thereof; and,

FIG. 6 is a rear view thereof.

The broken lines shown in FIG. 5 represent the border between claimed subject matter and unclaimed subject matter and form no part of the claimed design. The top view is not part of the claimed design. And the broken line rectangle in FIGS. 1 and 2 represents environmental subject matter which is also not part of the claimed design.