The ornamental design for an mountingfixture for a light, as shown and described.
FIG. 1 is a lower perspective view of the mounting fixture for a light of the present invention showing my new design, the mounting fixture being in an extended configuration;
FIG. 2 is a first side view of the mounting fixture for a light in the extended configuration;
FIG. 3 is a top view of the mounting fixture for a light in the extended configuration;
FIG. 4 is a second side view of the mounting fixture for a light in the extended configuration, the second side view being opposite the first side view;
FIG. 5 is a front view of the mounting fixture for a light in the extended configuration;
FIG. 6 is a rear view of the mounting fixture for a light in the extended configuration;
FIG. 7 is a bottom view of the mounting fixture for a light in the extended configuration;
FIG. 8 is a lower perspective view of the mounting fixture for a light, the mounting fixture being in a retracted configuration; and,
FIG. 9 is a first side view of the mounting fixture for a light in the retracted configuration.
The broken lines in the drawings illustrate features that form no part of the claimed design.