Such a cheque will bounce up and down (3)
I believe the answer is:
'up and down' is the definition.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for dud that I've seen before include "Ineffectual person" , "Forged" , "Failing in its function" , "Explosive not detonating" , "Fake -- failure" .)