The ornamental design for a portion of a camera, as shown and described.
FIG. 1 is a front perspective view of a portion of a camera showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a left side view thereof; and,
FIG. 5 is a right side view thereof.
The broken line showing of the remainder of the camera is for illustrative purposes only and forms no part of the claimed design. The stippling on the ring-shaped region and lines radiating out therefrom is used herein to illustrate illumination of the ring-shaped region.