The most common and most likely answer to this crossword clue is the 9 letter word GYROSCOPE
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More clues leading to the result GYROSCOPE
Buddy explains!
The straight part
We know that "device in a plane" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case device in a plane = gyroscope.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 GYROSCOPE mean?
GYROSCOPE noun- An apparatus composed of a wheel which spins inside of a frame (gimbal) and causes the balancing of the frame in any direction or position. In the form of a gyroscopic stabilizer, used to help keep aircraft and ships steady.