Physical structure (7)
I believe the answer is:
anatomy
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">physical structure</span>' is the definition.<br/ ><span class="explanation-format__explanation">(an animal's anatomy is its physical structure)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for anatomy that I've seen before include "Scientific study of bodily structure" , "Study of body structure" , "Study of the structure of animals" , "Study of bodies" , "Study of animal structures" .)