Clue: Decisive strike with daring German spirit (6)
Answer: KOBOLD
Explanation: Definition: German spirit
A charade of KO (knock out, 'decisive strike') plus BOLD ('daring'), for a German goblin – and the derivation of cobalt; early attempts to smelt cobalt ores were unsuccessful, producing a noxious smoke from the contained arsenic, which was attributed to the work of a goblin.