Unventilated (7)
I believe the answer is:
airless
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unventilated</span>' is the definition.<br/ ><span class="explanation-format__explanation">(similar in meaning)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for airless that I've seen before include "Still" , "Close" , "Unventilated" , "Lacking ventilation" , "not a breath of wind" .)