Immediately make amends round about (2,4)
I believe the answer is:
at once
'immediately' is the definition.
(thesaurus)
'make amends round about' is the wordplay.
'make amends' becomes 'atone' (I've seen this before).
'round' is an insertion indicator.
'about' becomes 'c' (abbreviation for 'circa').
'atone' enclosing 'c' is 'AT ONCE'.
(Other definitions for at once that I've seen before include "'Immediately (2,4)'" , "This instant, without delay" , "Right now, this instant" , "without hesitation" , "This minute!" .)