Empty out (4)
(Other definitions for teem that I've seen before include "pelt" , "Rain cats and dogs" , "Move in large numbers" , "Seethe" , "(Of rain) pour down" .)
'empty out' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for drain that I've seen before include "Waste pipe" , "Wasted down here" , "Waste channel/pipe" , "Deprive gradually of strength or resources" , "Gutter" .)