Sour liquid (7)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sour liquid</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 vinegar that I've seen before include "Acetic acid" , "Ill-temper" , "Salad dressing" , "Liquid used as condiment or food preservative" , "Sour liquid used as condiment" .)
(Other definitions for acid that I've seen before include "It is neutralized by alkali" , "Chemical compound" , "Bitter or sour" , "Caustic liquid of many kinds" , "Cutting" .)