Organic catalyst (6)
I believe the answer is:
enzyme
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">organic catalyst</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 enzyme that I've seen before include "Protein produced by living cells" , "Protein product of living cells" , "It acts as a catalyst to bring about biochemical reaction" , "Protein substance acting as a catalyst" , "Substance created in living cells acting as a catalyst" .)