Open, as a keg (3)
I believe the answer is:
tap
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">open as a keg</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tap that I've seen before include "that's less hard than 11 [BASH] or 22 [BATTER]" , "water supply" , "Intercept; light knock" , "Somewhere to drink beer" , "Flow controller; knock" .)