The ornamental design for a fan for a garment, as shown and described.
FIG. 1 is a front, top and right-side perspective view of a fan for a garment showing my new design;
FIG. 2 is a rear, top and left-side perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof;
FIG. 7 is a right-side view thereof;
FIG. 8 is a left-side view thereof; and,
FIG. 9 is a perspective view shown in a state of use.
The broken lines shown represent portions of the fan for a garment and environmental structure. None of the broken lines form part of the claimed design.