Vapour from boiling water (5)
I believe the answer is:
steam
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vapour from boiling water</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 steam that I've seen before include "Pre-digital" , "Gas formed by vaporizing water at 100?C" , "Cook" , "Kind of power" , "Kettle emission" .)