Criminal's anxiety in German (8)
I believe the answer is:
gangster
'criminal's' is the definition.
(gangster is a kind of criminal)
'anxiety in german' is the wordplay.
'anxiety' becomes 'angst' (Angst is an example).
'in' means one lot of letters goes inside another.
'german' becomes 'ger' (abbreviation).
'angst' inserted into 'ger' is 'GANGSTER'.
(Other definitions for gangster that I've seen before include "One of the mob, like Al Capone" , "Hood, desperado" , "Member of criminal mob" , "Hoodlum" , "Member of a mob like Al Capone" .)