With sulphur and charcoal, can be explosive! (5)
I believe the answer is:
nitre
'be explosive' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for nitre that I've seen before include "what goes into bangers" , "explosive component" , "Chemical" , "explosive ingredient" , "Mineral used in gunpowder" .)