Make amends and leave in a single attempt (2,3,2)
I believe the answer is:
at one go
'in a single attempt' is the definition.
(I've seen this in another clue)
'make amends and leave' is the wordplay.
'make amends' becomes 'atone' (to atone is to make amends for a wrong deed).
'and' means one lot of letters go next to another.
'leave' becomes 'go' (to go is to depart or leave).
'atone'+'go'='AT ONE GO'
(Other definitions for at one go that I've seen before include "First time" , "simultaneously" , "In a single attempt or visit" .)