I claim the ornamental design for a broom, as shown and described.
FIG. 1 is a front view of my design for a broom;
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 top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a perspective view in an environment of use.
The broken lines appearing in FIG. 7 depict an animal which is environmental subject matter that forms no part of the claimed design. The broken lines in the broom depict stitching and is considered part of the claimed design.