### Clue: Exploding slug sounds doubly stupid when hit by train (6,6)
### Answer: DUMDUM BULLET 
 ### Explanation: Definition: Exploding slug
  DUMDUM{**homophone of** (sounds) "dumb"(stupid) twice,doubly} plus(when hit by) BULLET(train, the Shinkansen in Japan that runs at maximum speeds of 240-300 kph
Defn:  A lethal soft- or hollow-nosed slug,slang for bullet, that expands,explodes on impact and causes extensive laceration, named after Dum-Dum, a town near Kolkata, India where these bullets were made in the 19C.