Thighbone (5)
I believe the answer is:
femur
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thighbone</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for femur that I've seen before include "Thighbone" , "Large bone" , "Thigh bone" , "bit of leg" , "Part of leg" .)