The ornamental design for a slide for a firearm, as shown and described.
FIG. 1 is a top perspective view of a slide for a firearm in accordance with the new design;
FIG. 2 is a left-side view of the slide for a firearm of FIG. 1;
FIG. 3 is a right-side view of the slide for a firearm of FIG. 1;
FIG. 4 is a front view of the slide for a firearm of FIG. 1;
FIG. 5 is a rear view of the slide for a firearm of FIG. 1; and,
FIG. 6 is a top view of the slide for a firearm of FIG. 1.
The broken lines in the figures are directed to portions of a firearm that form no part of the claim. The shaded surfaces in the figures form part of the claim.