Volume decreased by accountant, when assistant leaves in panic, having an explosive nature (8)
I believe the answer is:
volcanic
'assistant leaves in panic having an explosive nature' is the definition.
I can't tell whether this definition defines the answer.
'volume decreased by accountant' is the wordplay.
'volume' becomes 'vol' (abbreviation).
'decreased' becomes 'nic' (I can't explain this - if you can you should believe this answer much more).
'by' is a charade indicator (letters next to each other).
'accountant' becomes 'CA' (abbreviation for chartered accountant).
'nic' after 'ca' is 'canic'.
'vol'+'canic'='VOLCANIC'
'when' is the link.
Can you help me to learn more?
(Other definitions for volcanic that I've seen before include "Liable to erupt" , "Relating to mountains such as Vesuvius" , "given to sudden outbursts" , "Like pumice" , "Relating to fissures which produce lava" .)