They make things happen (9)
I believe the answer is:
catalysts
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">they make things happen</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for catalysts that I've seen before include "They cause things to happen" , "They precipitate change while remaining the same" , "They cause change" .)