Respiratory organs (5)
I believe the answer is:
lungs
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">respiratory organs</span>' is the definition.<br/ ><span class="explanation-format__explanation">(lung is a kind of respiratory organ)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for lungs that I've seen before include "Air bags" , "Breathing apparatus" , "Respiratory organs" , "Breathing organs" , "Animal organs" .)