Emptied (7)
(Other definitions for drained that I've seen before include "empty" , "Emptied of liquid" , "Exhausted" , "spent" , "Deprived of strength" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">emptied</span>' is the definition.<br/ ><span class="explanation-format__explanation">('vacate' can be a synonym of 'empty')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Another definition for vacated that I've seen is " Quitted".)