The ornamental design for a portion of a footwear upper, as shown and described.
FIG. 1. is a top front perspective view of a portion of a footwear upper embodying the new design;
FIG. 2. is a right side elevational view thereof; and,
FIG. 3. is a left side elevational view thereof.
FIG. 1–3 show features of an article of footwear in phantom lines. These features are shown for environmental purposes and do not form any part of the claimed design.