Sacks carrying trade explosives (9)
I believe the answer is:
fireworks
'sacks carrying trade explosives' is the definition.
I can't judge whether this defines the answer.
'sacks carrying trade explosives' is the wordplay.
'sacks' becomes 'fires' ('fire' can be a synonym of 'sack').
'carrying' is an insertion indicator.
'trade explosives' becomes 'work' (I can't explain this - if you can you should believe this answer much more).
'fires' placed around 'work' is 'FIREWORKS'.
Can you help me to learn more?
(Other definitions for fireworks that I've seen before include "rockets, perhaps" , "Display on November 5th etc" , "Pyrotechnics" .)