The most common and most likely answer to this crossword clue is the 4 plus 4 letter word DEAD DUCK
D
E
A
D
D
U
C
K
More clues leading to the result DEAD DUCK
- Deal endlessly with Germany over zilch? It’s doomed to failure
- No longer important to avoid as it’s defunct
- After brown bread, nothing is a lost cause
- Passed on zip that doesn’t work
- Individually do something with no chance of success
- Completely put under water, it has no chance of success
- One doomed floor stocked with total uranium
- Hopeless plan to take late dip?
Buddy explains!

The straight part
We know that "that doesn’t work" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that doesn’t work = dead duck.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.