Laugh at mine and go away (3,2)
I believe the answer is:
hop it
'go away' is the definition.
(I've seen this before)
'laugh at mine' is the wordplay.
'laugh' becomes 'ho' (representation of a laughing sound).
'at' means one lot of letters go next to another.
'mine' becomes 'pit' (down the pit).
'ho'+'pit'='HOP IT'
'and' acts as a link.
(Other definitions for hop it that I've seen before include "get lost" , "Scram!" , "shove off" , "Skedaddle!" , "Leave" .)