Substance used for setting jams and jellies (6)
I believe the answer is:
pectin
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">substance used for setting jams and jellies</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 pectin that I've seen before include "Setting agent needed in jams" , "It thickens jam" , "Jam setter" , "Component of jam" , "Ingredient for setting jam" .)