The ornamental design for a hat with a pocket, as shown and described.
FIG. 1 is a perspective view of a hat with a pocket, wherein the hat is pictured right-side out.
FIG. 2 is a cross-sectional view of the hat with a pocket along line 2-2 of FIG. 1.
FIG. 3 is a perspective view of the hat with a pocket, wherein the hat is pictured inside out.
FIG. 4 is a front elevation view thereof.
FIG. 5 is a back elevation view thereof.
FIG. 6 is a left side elevation view thereof.
FIG. 7 is a right side elevation view thereof.
FIG. 8 is a top plan view thereof; and,
FIG. 9 is a bottom plan view thereof.
The dashed lines in the drawings define the bounds of the claimed design and forms no part thereof. The dot-dash lines in the drawings illustrate the environment of the claimed design and form no part thereof.