The ornamental design for a frame, as shown and described.
FIG. 1 is a front elevational view of a frame showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is front elevational view thereof;
FIG. 4 is rear elevational view thereof;
FIG. 5 is side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines in FIGS. 1 and 2 are to show environment and form no part of the claimed design. The additional broken lines shown in FIGS. 2-7 are to show portions of the frame, which form no part of the claimed design.