Sign of something about to happen (7)
I believe the answer is:
portent
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sign of something about to happen</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 portent that I've seen before include "Augury" , "Prophetic sign" , "Sign, omen" , "Sign or warning of an event likely to happen" , "Foreboding" .)