Slick German party (4)
I believe the answer is:
glib
'slick' is the definition.
(I know that slick can be written as glib)
'german party' is the wordplay.
'german' becomes 'g' (abbreviation).
'party' becomes 'lib' (abbreviation for Liberal, uk political party).
'g'+'lib'='GLIB'
(Other definitions for glib that I've seen before include "slick in speech" , "Insincere, shallow" , "Of speech, facile but insincere" , "Slippery in speech" , "Smooth-tongued" .)