We claim the ornamental design for a cover for an electronic device, as shown and described.
FIG. 1 is a front perspective view of a cover for an electronic device showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a rear perspective view thereof;
FIG. 9 is a right-side view of the cover for an electronic device in which a camera lens is provided in broken lines to illustrate an example environment; and,
FIG. 10 is a rear perspective view of the cover for an electronic device in which a camera lens is provided in broken lines to illustrate an example environment.
The broken lines in the figures depict environmental subject matter and form no part of the claimed design.