Barley used in brewing (4)
I believe the answer is:
malt
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">barley used in brewing</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 malt that I've seen before include "Cereal grain for distilling" , "Brewing ingredient derived from grain" , "strong drink" , "Barley product used in brewing" , "Ingredient of beer" .)