The most common and most likely answer to this crossword clue is the 9 letter word EDUCATION
I've seen this crossword clue in Financial Times
E
D
U
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More clues leading to the result EDUCATION
- Long time to bank old money with one for guidance
- Teaching English and Latin could flop after lecturers are expelled
- What might be ridiculous to a dunce and I?
- Change actioned to accommodate uniform – right for children?
- European motorbike company supported by viable training
- Due to ANC, I abandoned schooling
- Guidance given by leading journalist exercising caution
- European professor goes round Utica recklessly providing instruction
- Drilling area protected by exhaust
- Auntie and doctor not half wrong — child’s right!
Buddy explains!

The straight part
We know that "What might be ridiculous to a dunce and I?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what might be ridiculous to a dunce and i? = education.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 EDUCATION mean?
EDUCATION noun- The process of imparting knowledge, skill and judgment.
- Facts, skills and ideas that have been learned, either formally or informally.