I claim the ornamental design for a one-piece encircling anchor, as shown and described.
FIG. 1 is a perspective view of a one-piece encircling anchor showing my new design;
FIG. 2 is a side elevational view thereof showing the one-piece encircling anchor in use, the elevational view of the opposing side being a mirror image thereof; the broken lines depict environmental structure for illustrative purposes only and form no part of the claimed design;
FIG. 3 is an end elevational view thereof;
FIG. 4 is an elevational view of the opposing end thereof showing the one-piece encircling anchor in use; the broken lines depict environmental structure for illustrative purposes only and form no part of the claimed design;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof; and,
FIG. 7 is a side elevational view of the one-piece encircling anchor prior to assembly thereof.