In the historical sense, old Greek child-killer to return from America (9)
I believe the answer is:
herodotus
'in the historical sense old greek' is the definition.
I can't tell whether this definition defines the answer.
'child-killer to return from america' is the wordplay.
'child killer' becomes 'herod' (I can't justify this - if you can you should give a lot more credence to this answer).
'return' shows that the letters should be reversed in order.
'from america' becomes 'us'.
'to' in reverse letter order is 'ot'.
'herod'+'ot'+'us'='HERODOTUS'
Can you help me to learn more?
(Other definitions for herodotus that I've seen before include "Old Greek" , "Famous Greek" , "Ancient Greek historian" , "Historical pioneer" .)