The ornamental design for a supportbracket for a column, as shown and described.
FIG. 1 is an isometric view showing the top, front, and left side of an ornamental design for a support bracket for a column;
FIG. 2 is an isometric view showing the top, rear, and right side of the support bracket for a column of FIG. 1;
FIG. 3 is a three dimensional view showing the top, front, and left side of the ornamental design of the support bracket for a column of FIG. 1, FIG. 3 being rotated out of the FIG. 1 isometric axis to show five struts extending between the top plate and base plate of the support bracket for a column;
FIG. 4 is an isometric view showing the bottom, front, and left side of the support bracket for a column of FIG. 1; and,
FIG. 5 is a top plan view of the support bracket for a column of FIG. 1 with the top plate removed to show the location of the five struts that extend between the support bracket top plate and base plate.