The most common and most likely answer to this crossword clue is the 9 letter word FACETIOUS
I've seen this crossword clue in The Times
F
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More clues leading to the result FACETIOUS
- What is true about English I love, America being flippant?
- Playful aspect of promissory notes
- Waggish fellow, one with crumpled suit with old contents
- Amusing aspects will include debt
- Confront first of teenagers with evidence of debts, being sarcastic?
- Flip ace of suit out of sequence
- Inappropriately funny to confront journalist leaving flat
- Look out! Is it becoming funny?
- Regard admissions of debt as flippant
Buddy explains!

The straight part
We know that "flippant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flippant = facetious.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 FACETIOUS mean?
FACETIOUS adjective- Treating serious issues with (often deliberately) inappropriate humour; flippant.
- Pleasantly humorous; jocular.