The ornamental design for a lid for a container, as shown and described.
FIG. 1 is a top perspective view of the design of a lid for a container showing the new design;
FIG. 2 is a top plan view of the lid for a container shown in FIG. 1;
FIG. 3 is a bottom plan view of the lid for a container shown in FIG. 1;
FIG. 4 is a right side elevation view of the lid for a container shown in FIG. 1; and,
FIG. 5 is a front elevation view of the lid for a container shown in FIG. 1.
The features shown in broken lines depict environmental subject matter only and form no part of the claimed design. The boundary line depicted as a long dash-short dash-short dash-long dash line defines the boundary of the claimed design and forms no part thereof.