I claim the ornamental design for a waistband, as shown and described.
FIG. 1 is a rear elevational view of a rear portion of a waistband in accordance with the new design, depicting a tab extension centrally aligned on a rear side of the waistband; and,
FIG. 2 is a front elevational view of the waistband of FIG. 1, depicting the tab extension located on the rear portion of the waistband.
In the drawing, the dashed lines indicate environmental structure and form no part of the claimed design, and any portions of the waistband not shown form no part of the claimed design.