Nostrils (5)
I believe the answer is:
nares
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nostrils</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for nares that I've seen before include "space to breathe" , "The nostrils" , "Breathers in anatomy class" .)