Take in air (7)
I believe the answer is:
breathe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">take in air</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 breathe that I've seen before include "Take into mouth" , "Draw air into, and expel out of, the lungs" , "Absorb air" , "Take air in and out of the lungs" , "use aqualungs, perhaps" .)