Stud began experimenting with German diet (9)
I believe the answer is:
bundestag
'german diet' is the definition.
(German parliament - diet can mean a parliament)
'stud began experimenting' is the wordplay.
'experimenting' is an anagram indicator.
'stud'+'began'='studbegan'
'studbegan' with letters rearranged gives 'BUNDESTAG'.
'with' is the link.
(Other definitions for bundestag that I've seen before include "German parliament building" , "house in Germany" , "German diet" , "German house" .)