The most common and most likely answer to this crossword clue is the 14 letter word SCATTERBRAINED
I've seen this crossword clue in The Times
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More clues leading to the result SCATTERBRAINED
- Frivolous broadcast about black cats and dogs?
- Describe tartan design as silly
- Feline in street showing hesitation gets hit on head and becomes forgetful
- Throw water into crash site? Silly
- Careless bird nears cat, mad about tea mostly
- Unfocused brat creates din, needing to be sorted out
- Disorganised spread knocked on the head
- Sow border with input from water in the clouds?
- Bartender’s act I misconstrued as disorganised
- Thoughtless broadcast knocked on the head
Buddy explains!

The straight part
We know that "Frivolous" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case frivolous = scatterbrained.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 SCATTERBRAINED mean?
SCATTERBRAINED adjective- Having the qualities of a scatterbrain: absent-minded, forgetful, easily distracted.