The most common and most likely answer to this crossword clue is the 3 letter word COD
I've seen this crossword clue in Independent
C
O
D
More clues leading to the result COD
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The straight part
We know that "joke" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case joke = cod.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does COD mean?
COD noun- A small bag or pouch.
- A husk or integument; a pod.
- The scrotum (also in plural).
- A pillow or cushion.
- The Atlantic cod, Gadus morhua.
- The sea fish of the genus Gadus generally, as inclusive of the Pacific cod (Gadus macrocephalus) and Greenland cod (Gadus ogac or Gadus macrocephalus ogac).
- The sea fish of the family Gadidae which are sold as "cod", as haddock (Melanogrammus aeglefinus) and whiting (usually Merlangius merlangus).
- (usually with qualifiers) Other unrelated fish which are similarly important to regional fisheries, as the hapuku and cultus cod.
- (usually with qualifiers) Other unrelated fish which resemble the Atlantic cod, as the rock cod (Lotella rhacina) and blue cod (Parapercis colias).
- A joke or an imitation.
- A stupid or foolish person.
- To attempt to deceive or confuse.
- Having the character of imitation; jocular. (now usually attributive, forming mostly compound adjectives).
- Bad.