European in wealthy German state (5)
I believe the answer is:
reich
'german state' is the definition.
(as in the Third Reich)
'european in wealthy' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'in' indicates putting letters inside.
'wealthy' becomes 'rich' (similar in meaning).
'e' placed into 'rich' is 'REICH'.
(Other definitions for reich that I've seen before include "It was twelve" , "Third of a thousand years" , "Nazi empire" , "Old German state" , "Hitler's was the Third" .)