Complicated for a technician, unleashing loud chemical process? (5,8)
I believe the answer is:
chain reaction
'chemical process?' is the definition.
(chain reaction is a kind of chemical process)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for chain reaction that I've seen before include "process hard to stop" , "Series of consequences" , "Sequence" , "Series of events each caused by the previous one" , "Series of linked events" .)