Time to abandon bet? That’s a joke (3)
I believe the answer is:
pun
'that's a joke' is the definition.
(pun is a type of joke)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for pun that I've seen before include "A play on words - not the height of wit" , "conceit by a wordsmith?" , "Bit of paronomasia; witticism" , "A play on words, perhaps the lowest form of wit" , "A play on words, not really wit" .)