Bones, anatomically (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">bones anatomically</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 ossa that I've seen before include "mountain in Thessaly" , "Legendary mountain" , "Technical name for bones" , "famous mount" , "To pile Pelion upon - is to make even greater" .)