Leave mine at the back of the house (3,2)
I believe the answer is:
hop it
'leave' is the definition.
(to hop it is to leave quickly)
'mine at the back of the house' is the wordplay.
'mine' becomes 'pit' (down the pit).
'at the back of' is a charade indicator (letters next to each other).
'the house' becomes 'ho' (abbreviation for house).
'pit' after 'ho' is 'HOP IT'.
(Other definitions for hop it that I've seen before include "get lost" , "Skedaddle!" , "Clear off!" , "On your bike!" , "Get away!" .)