Sauce base (4)
I believe the answer is:
roux
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sauce base</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 and flour mixture, cooked and used to make sauces" , "Mixture of flour and fat for cooking" , "Thickener for sauces" , "Fat, flour sauce base" , "Mixture of butter and flour used for sauces" .)