The ornamental design for a headstock for an electronicinstrument, as shown and described.
FIG. 1 is a front, left side perspective view of a headstock for an electronic instrument showing my new design;
FIG. 2 is a back, right side perspective view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a back view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a partially enlarged front, left side perspective view thereof, taken from FIG. 1.
The lightweight broken lines show unclaimed subject matter only and form no part of the claimed design. The heavyweight broken line squares that appear in FIGS. 1 and 9 are included for the purpose of showing partially enlarged views only and form no part of the claimed design.