Patella (7)
I believe the answer is:
kneecap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">patella</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for kneecap that I've seen before include "one going on bender?" , "Joint protection" , "The informal patella (7)" , "part of joint" , "Bone" .)