The most common and most likely answer to this crossword clue is the 7 letter word APHASIA
I've seen this crossword clue in The Guardian
A
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More clues leading to the result APHASIA
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The straight part
We know that "being 24" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case being 24 = aphasia.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 APHASIA mean?
APHASIA noun- A partial or total loss of language skills due to brain damage. Usually, damage to the left perisylvian region, including Broca's area and Wernicke's area, causes aphasia.