Set off, incite (5)
I believe the answer is:
spark
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">set off</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >'<span class="explanation-format__original">incite</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ ></span>
(Other definitions for spark that I've seen before include "Small electric flash" , "Fragment of a burning substance" , "Clever person" , "bit of fire?" , "Glowing particle" .)