Element in bones (7)
I believe the answer is:
calcium
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">element in bones</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for calcium that I've seen before include "Chemical element in bones, basis of lime" , "White metallic element found in most animals and plants, Ca" , "Bone constituent" , "Atomic number 20" , "Element, component of bones and teeth" .)