The windpipe (7)
I believe the answer is:
trachea
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">the windpipe</span>' is the definition.<br/ ><span class="explanation-format__explanation">('trachea' can be a synonym of 'windpipe')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for trachea that I've seen before include "where air passes" , "membranous tube" , "It connects the larynx and bronchi" , "Breathing tube" , "Tube taking inhaled air from the larynx" .)