Bone of the forearm (4)
I believe the answer is:
ulna
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bone of the forearm</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ulna that I've seen before include "The longer and inner bone in forearm" , "Thinner of two long bones in forearm" , "Inner bone of the human forearm" , "One of two bones of the forearm" , "Long bone in the arm" .)