Portion of a tractor

FIG. 1 is a right side view of a portion of a tractor showing our new design;

FIG. 2 is a left side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is an upper right front perspective view thereof;

FIG. 6 is an enlarged front view thereof; and,

FIG. 7 is an enlarged upper right front perspective view thereof.

The portions of FIGS. 1-7 shown in coarse dot pattern and outlined in dashed lines form no part of the claimed design.

A bottom view is omitted because it is plain and unornamental and forms no part of the subject matter of the claimed design.