The most common and most likely answer to this crossword clue is the 9 letter word SHIFTIEST
I've seen this crossword clue in Financial Times
S
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F
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Buddy explains!
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 SHIFTIEST mean?
SHIFTIEST adjective- Subject to frequent changes in direction.
- (of a person's eyes) Moving from one object to another, not looking directly and steadily at the person with whom one is speaking.
- Having the appearance of being dishonest, criminal or unreliable.
- Resourceful; full of, or ready with, shifts or expedients.