Corrosive substance (4)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">corrosive substance</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 acid that I've seen before include "Corrosive fluid" , "Corrosive substance" , "See 4 Across" , "Substance with pH of less than 7" , "Bitter; biting" .)
(Other definitions for lime that I've seen before include "Round green fruit or a linden tree" , "Hang about in Jamaica" , "White substance used in cement" , "Greene character?" , "Sharp-tasting fruit" .)
(Other definitions for alkali that I've seen before include "Compound like lime" , "Substance turning litmus paper blue" , "In pH terms, not acid" , "Chemical base" , "Opposite of acid" .)