The ornamental design for an anchor, as shown and described.
FIG. 1 is a perspective view of a anchor showing my new design, the broken
lines are for illustrative purposes only and form no part of the claimed
design;
FIG. 2 is a right side elevational view which is a mirror image of the left
side;
FIG. 3 is a bottom plan view;
FIG. 4 is a top plan view; and,
FIG. 5 is a front elevational view which is a mirror image of the rear view
.