Fire indicator (5)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fire indicator</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 smoke that I've seen before include "Carbon vapour" , "Cure (meat) over fire" , "Cure (food) - endanger health!" , "Use cigarettes" , "Cure (eg, herring)" .)