Clear out drain (3,3)
I believe the answer is:
run off
This clue is a double definition.
'clear out' is the first definition.
(thesaurus)
'drain' is the second definition.
(I've seen this before)
(Other definitions for run off that I've seen before include "Rain draining from an area" , "Make copies" , "Further contest to decide a tie" , "Drain" , "Further contest; drainage" .)