The most common and most likely answer to this crossword clue is the 8 letter word TRUSTING
I've seen this crossword clue in Financial Times
T
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T
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More clues leading to the result TRUSTING
Buddy explains!

The straight part
We know that "Naive" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case naive = trusting.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 TRUSTING mean?
TRUSTING verb- To place confidence in; to rely on, to confide, or have faith, in.
- To give credence to; to believe; to credit.
- To hope confidently; to believe (usually with a phrase or infinitive clause as the object)
- To show confidence in a person by entrusting them with something.
- To commit, as to one's care; to entrust.
- To give credit to; to sell to upon credit, or in confidence of future payment.
- (followed by to) To rely on (something), as though having trust (on it).
- To risk; to venture confidently.
- To have trust; to be credulous; to be won to confidence; to confide.
- To sell or deliver anything in reliance upon a promise of payment; to give credit.
- Inclined to believe what others say; trustful