Lung contents
I believe the answer is:
air
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">lung contents</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for air that I've seen before include "Song - atmosphere" , "Tune or aura" , "If it's hot, it's boastful" , "Region above the ground" , "Vital thing" .)