The most common and most likely answer to this crossword clue is the 9 letter word FREQUENCY
I've seen this crossword clue in The Guardian
F
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More clues leading to the result FREQUENCY
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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 FREQUENCY mean?
FREQUENCY noun- The rate of occurrence of anything; the relationship between incidence and time period.
- The property of occurring often rather than infrequently.
- The quotient of the number of times n a periodic phenomenon occurs over the time t in which it occurs: f = n / t.
- Number of times an event occurred in an experiment (absolute frequency)