The term 'PART OF A SKELETON' can be answered with two crossword solutions: BONE and ULNA. Bones are the hard, rigid structures that make up the skeleton of vertebrates. They provide support for the body, protect internal organs, and allow movement. The ULNA is one of the two bones in the forearm, located on the medial side of the arm. It is the larger of the two bones and connects to the humerus at the elbow joint.