The most common and most likely answer to this crossword clue is the 9 letter word FLIP-FLOP
I've seen this crossword clue in The Guardian
F
L
I
P
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F
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Buddy explains!
The straight part
We know that "a complete change of direction!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a complete change of direction! = flip-flop.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 FLIP-FLOP mean?
FLIP-FLOP noun- An instance of flip-flopping, of repeatedly changing one's stated opinion about a matter.
- A bistable; an electronic switching circuit that has either two stable states (switching between them in response to a trigger) or a stable and an unstable state (switching from one to the other and back again in response to a trigger), and which is thereby capable of serving as one bit of memory.
- A sandal consisting of a rubber sole fastened to the foot by a rubber thong fitting between the toes and around the sides of the foot.
- A change of places; an inversion or swap.
- The sound of a regular footfall.
- To alternate back and forth between directly opposite opinions, ideas, or decisions.