The ornamental design for a headlamp for a vehicle, as shown.
FIG. 1 is a top perspective view of a headlamp for a vehicle, showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right-side elevation view thereof; and,
FIG. 4 is a top plan view thereof.
The broken lines in the figures depict environmental subject matter and form no part of the claimed design.
The front outer cover of the environmental headlight is clear and environmental contour lines are visible as the projection lenses are visible through the clear front outer cover.
The figures represent the right headlamp for a vehicle, the left headlamp for a vehicle is a mirror image thereof.