Weapon going wrong held by the German (9)
I believe the answer is:
derringer
'weapon' is the definition.
(derringer is a kind of weapon)
'going wrong held by the german' is the wordplay.
'going wrong' becomes 'erring' (I've seen this before).
'held by' is an insertion indicator.
'the german' becomes 'der' ('the' in German).
'erring' put into 'der' is 'DERRINGER'.
(Other definitions for derringer that I've seen before include "Small pistol used by gamblers in western films" , "Weapon" , "Pocket pistol" , "Short-barrelled American pistol" .)