The most common and most likely answer to this crossword clue is the 12 letter word DISORIENTATE
I've seen this crossword clue in Financial Times
D
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S
O
R
I
E
N
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A
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More clues leading to the result DISORIENTATE
Buddy explains!

The straight part
We know that "As jet leg might" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case as jet leg might = disorientate.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 DISORIENTATE mean?
DISORIENTATE verb- To cause to lose orientation or direction.
- To confuse or befuddle.