Costal bone (3)
I believe the answer is:
rib
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">costal bone</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for rib that I've seen before include "Kid" , "joke" , "Supporting structure" , "Tease good-naturedly" , "Tease; pectoral bone" .)