Big beer order (3)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">big beer order</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 keg that I've seen before include "What's found at King's Head" , "Barrel as for beer" , "Sort of beer" , "Small cask or barrel" , "Small beer cask" .)