Sauce thickener (4)
I believe the answer is:
roux
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sauce thickener</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 roux that I've seen before include "Fat, flour sauce base" , "Thickener for sauces" , "Mixture of fat and flour used as a base for sauces" , "Butter/flour mix" , "Butter and flour sauce combination" .)