Smoke outlet (4)
(Other definitions for flue that I've seen before include "smoky passage" , "Chimney duct" , "Smoke duct" , "Conduit for smoke" , "Outlet for smoke or gas" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">smoke outlet</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for chimney that I've seen before include "A cleft for climbing" , "Smoke outlet" , "Smoke pipe; rock cleft" , "Smoke vent" , "Flue" .)