We claim the ornamental design for a grip for a writing instrument, as shown and described.
FIG. 1 is a perspective view of a grip for a writing instrument showing our new design;
FIG. 2 is a front view of FIG. 1;
FIG. 3 is a back view of FIG. 1;
FIG. 4 is a right side view of FIG. 1, the left side view being a mirror image of the right side view;
FIG. 5 is a top view of FIG. 1;
FIG. 6 is a bottom view of FIG. 1; and,
FIG. 7 is a close up view of a portion of FIG. 2.
Portions of the writing instrument and the environment shown in broken lines are for the purpose of showing features that form no part of the claimed design.
The stippling represents contrast in material and not texture or color.