Kind of acid in a lemon (6)
I believe the answer is:
citric
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">kind of acid in a lemon</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 citric that I've seen before include "Relating to, eg, 5 across" , "Derived from oranges, lemons, etc" , "Derived from eg, lemon" , "Fruity" , "Acid of oranges and lemons" .)