Kind of acid in vinegar (6)
I believe the answer is:
acetic
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">kind of acid in vinegar</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for acetic that I've seen before include "Colourless pungent acid" , "Saucy'" , "in relation to acid" , "Like vinegar's acid" , "The acid in vingear" .)