Odor sensor (4)
I believe the answer is:
nose
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">odor sensor</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for nose that I've seen before include "Nuzzle" , "See 7" , "Flair (for wine)" , "Informer" , "Organ of smell" .)