We hear unique German article a marvel (6)
I believe the answer is:
wonder
'a marvel' is the definition.
('wonder' can be a synonym of 'marvel')
'we hear unique german article' is the wordplay.
'we hear' indicates a 'sounds like' (homophone) clue.
'unique' becomes 'one' (synonyms).
'german article' becomes 'der' (definite article in German).
'one' sounds like 'won'.
'won'+'der'='WONDER'
(Other definitions for wonder that I've seen before include "Ponder" , "Marvellous person; feel doubt" , "Marvel or question" , "Something amazing" , "amazement" .)