Draining device (6)
I believe the answer is:
siphon
'draining device' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for siphon that I've seen before include "Bottle from which a liquid is forced by pressure of gas" , "Tube used to draw a liquid" , "Tube used to remove liquid from a higher to a lower level" , "A bottle that squirts, say soda water" , "Tube down which liquid flows unaided" .)