Thin down (6)
I believe the answer is:
dilute
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">thin down</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dilute that I've seen before include "Adulterate" , "not neat" , "Add liquid to lessen strength" , "Add water to thin" , "Reduce in strength or concentration" .)