In German, he's right again! (4)
I believe the answer is:
herr
'in german' is the definition.
'herr' can be an answer for 'german' (German equivalent to Mr). I'm unsure of the 'in' bit.
'he's right again' is the wordplay.
'right again' becomes 'rr' (I can't justify this - if you can you should give a lot more credence to this answer).
'he'+'rr'='HERR'
Can you help me to learn more?
(Other definitions for herr that I've seen before include "European guy" , "Form of address for German male" , "A German gentleman" , "German man's title" , "German form like Mr." .)