Breastbone (7)
I believe the answer is:
sternum
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">breastbone</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for sternum that I've seen before include "Breastbone" , "Human bone -- ten rums (anag)" , "Chest bone" , "Munster (anag.)" , "somewhere in chest" .)