The most common and most likely answer to this crossword clue is the 9 letter word DEPARTURE
D
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P
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R
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E
More clues leading to the result DEPARTURE
- Withdrawal of trade? Pure rubbish!
- Death shift
- Broadcast rude tape about king’s shift
- Going to put reader off
- Leaving shift
- Free trade with Peru? That’s something different
- Reader put out by Exodus
- In deep trouble, Arthur half-heartedly submitted resignation
- Breaking away from norm to replace new false tooth
- Taper rude, non-standard deviation
Buddy explains!

The straight part
We know that "retreat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case retreat = departure.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 DEPARTURE mean?
DEPARTURE noun- The act of departing or something that has departed.
- A deviation from a plan or procedure.
- A death.
- The distance due east or west made by a ship in its course reckoned in plane sailing as the product of the distance sailed and the sine of the angle made by the course with the meridian.
- The difference in easting between the two ends of a line or curve.
- The desertion by a party to any pleading of the ground taken by him in his last antecedent pleading, and the adoption of another.
- Division; separation; putting away.