The German caller produced a gun (9)
I believe the answer is:
derringer
'a gun' is the definition.
(I know that Derringer is a type of pistol)
'the german caller' is the wordplay.
'the german' becomes 'der' ('the' in German).
'caller' becomes 'ringer' (someone ringing someone on the phone).
'der'+'ringer'='DERRINGER'
'produced' acts as a link.
(Other definitions for derringer that I've seen before include "Short-barrelled American pistol" , "Weapon" , "Pocket pistol" , "Small pistol used by gamblers in western films" .)