Portion of a tractor

FIG. 1 is a front elevational view of a portion of a tractor, showing our design;

FIG. 2 is a rear elevational view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a right side elevational view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a top and right front perspective view thereof;

FIG. 7 is an enlarged front elevational view of an area labeled VII in FIG. 1 ; and,

FIG. 8 is an enlarged right side elevational view of an area labeled VIII in FIG. 4 .

All broken lines shown in the figures represent environmental structures and form no part of the claimed design.