Drain completely (5)
I believe the answer is:
empty
'drain completely' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for empty that I've seen before include "(Of words) insincere" , "Devoid of content" , "Like the sherry decanter by the time gran's jolly" , "Loneliness parents feel when their children leave home" , "Dead man" .)