The most common and most likely answer to this crossword clue is the 9 letter word MISGUIDED
I've seen this crossword clue in Financial Times
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More clues leading to the result MISGUIDED
Buddy explains!

The straight part
We know that "Deluded" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deluded = misguided.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 MISGUIDED mean?
MISGUIDED verb- To guide poorly or incorrectly.
- To lead astray; to lead into error.
- Ill-conceived or not thought through
- Misled or mistaken
- Lacking proper guidance