Nasal opening (7)
I believe the answer is:
nostril
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nasal opening</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 nostril that I've seen before include "Breathing channel" , "Aperture in nose" , "Through which one would snort" , "Breathing space" , "Bit of a breather" .)