The most common and most likely answer to this crossword clue is the 7 letter word NOONDAY
I've seen this crossword clue in The Times
N
O
O
N
D
A
Y
More clues leading to the result NOONDAY
- Number any do, possibly twelve
- Working twenty-four hours? At first no — twelve
- Twelve in number working diamonds, certainly
- Twelve years on, and zero changes
- No working period; time for lunch?
- Almost nobody died? Yes, twelve
- Time for lunch — it’s all off, apparently, 24 hours after
- Signal agreement holding on when sun is hottest
- Maybe Doris is behind drama being broadcast at this time?
- Nobody wanting English period at lunch time
Buddy explains!

The straight part
We know that "twelve" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case twelve = noonday.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 NOONDAY mean?
NOONDAY noun- The time of noon; the time of day when the sun is highest in the sky, especially on a hot day.
- The time of greatest prosperity.