I claim an ornamental design for a heel portion of footwear, as shown and described.
FIG. 1 is a rear perspective view of a heel portion of footwear showing the claimed design in association with the remainder of the footwear shown in broken lines;
FIG. 2 is a front perspective view thereof in association with the remainder of the footwear shown in broken lines;
FIG. 3 is a bottom perspective view thereof in association with the remainder of the footwear shown in broken lines; and,
FIG. 4 is a side view thereof in association with the remainder of the footwear shown in broken lines.