Separate chaff from grain (6)
I believe the answer is:
winnow
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">separate chaff from grain</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for winnow that I've seen before include "Blow air through (grain) to remove chaff" , "Separate the wheat from the chaff" , "Sift out" , "Fan" , "Dehusk grain using air currents" .)