How speedily you demonstrated the torch was working? (2,1,5)
I believe the answer is:
in a flash
'how' is the definition.
Both the definition and answer are adverbs. Maybe you can see a link between them that I can't see?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for in a flash that I've seen before include "How lightning appears" , "pictures may be taken" , "Very quickly" , "Instantly, straightaway" , "Almost instantly" .)