The ornamental design for a waistband for a garment, as shown and described.
FIG. 1 is a front view of a waistband for a garment according to the design;
FIG. 2 is a rear view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a front perspective view thereof;
FIG. 6 is a rear perspective view thereof;
FIG. 7 is a rear view thereof shown in an environment of use;
FIG. 8 is a top view thereof with the pocket thereof shown in a closed position; and,
FIG. 9 is a top view thereof with the pocket thereof shown in an opened position.
The portions of the garment shown in broken lines in FIGS. 1-9 do not form part of the claimed design. The broken line showing of the arms, torso, legs, and the item in the pocket of the waistband of the garment in FIG. 7 is for the purpose of illustrating portions of the environmental structure and forms no part of the claimed design.