Sharp taste (4)
I believe the answer is:
tang
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sharp taste</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 tang that I've seen before include "Pungency" , "Strong smell of gnat" , "Old dynasty" , "relish" , "Sharpness" .)