The most common and most likely answer to this crossword clue is the 8 letter word HYPNOSIS
I've seen this crossword clue in Independent
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More clues leading to the result HYPNOSIS
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The straight part
We know that "alternative therapy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case alternative therapy = hypnosis.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 HYPNOSIS mean?
HYPNOSIS noun- A trancelike state, artificially induced, in which a person has a heightened suggestibility, and in which suppressed memories may be experienced.
- The art or skill of hypnotism.