Crack line taken from Dickensian villain (4)
I believe the answer is:
quip
'crack' is the definition.
(both can mean a joke)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for quip that I've seen before include "Wisecrack" , "Witticism" , "Quick joke" , "Clever one-liner" , "Gibe" .)