The most common and most likely answer to this crossword clue is the 9 letter word JACKKNIFE
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More clues leading to the result JACKKNIFE
Buddy explains!

The straight part
We know that "dive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dive = jackknife.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 JACKKNIFE mean?
JACKKNIFE noun- A compact folding knife.
- The front-dive pike, in which the body folds and unfolds.
- A semi-trailer truck accident in which the vehicle mimics the closing of a jack-knife.
- To fold in the middle, as a jackknife does.
- To cause a semi-trailer truck to fold like a jackknife in a traffic accident.
- A resampling method that applies estimators to all subsamples that each omit a single different group (possibly of a single datapoint) of the original sample to provide a sample distribution of the estimate.