Invent noun with German cases (4)
I believe the answer is:
mint
'invent' is the definition.
(thesaurus)
'noun with german cases' is the wordplay.
'noun' becomes 'n'.
'with german' becomes 'mit'.
'cases' indicates putting letters inside.
'n' put inside 'mit' is 'MINT'.
(Other definitions for mint that I've seen before include "Aromatic plant - make money" , "Where money coins are made" , "Culinary herb" , "Building where coin money is made (4)" , "Money-making herb?" .)