### Clue: Explosive component can upset engineers (5)
### Answer: NITRE 
 ### Explanation: Definition: Explosive component
  Anagram/reversal(*upset*) of TIN(*can*) + RE($$R$$oyal *$$E$$ngineers*).  Defn:  Potassium (or sodium) nitrate, a powerful oxidising compound, hence its use as a *component* of *explosive* devices.