Leave house and topple over (3,2)
I believe the answer is:
hop it
'leave' is the definition.
(I've seen this before)
'house and topple over' is the wordplay.
'house' becomes 'ho' (abbreviation for house).
'and' means one lot of letters go next to another.
'topple' becomes 'tip'.
'over' says the letters should be written in reverse.
'tip' backwards is 'pit'.
'ho'+'pit'='HOP IT'
(Other definitions for hop it that I've seen before include "Run along now!" , "Clear off!" , "get lost" , "Skedaddle!" , "shove off" .)