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