That's wrong, sending back Japanese American (5)
I believe the answer is:
nisei
'japanese american' is the definition.
(I've seen this in another clue)
'that's wrong sending back' is the wordplay.
'that's' becomes 'ie'.
'wrong' becomes 'sin' (wrong can mean a sin or crime).
'sending back' says the letters should be written backwards.
'ie'+'sin'='iesin'
'iesin' back-to-front is 'NISEI'.
(Other definitions for nisei that I've seen before include "American born of Japanese immigrant parents" , "Second-generation immigrant" , "Type of American citizen" , "Child of immigrants" , "that's evil? The reverse" .)