Respiratory tube (7)
I believe the answer is:
trachea
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">respiratory tube</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for trachea that I've seen before include "get air supply through this" , "The formal windpipe" , "pipe" , "Tube carrying air to the lungs" , "Tube taking inhaled air from the larynx" .)