Cryptic crossword clue
Fast Sunday bike rider’s frenzy? I’m gripped by it! 12

The most common and most likely answer to this crossword clue is the 12 letter word QUADRAGESIMA

I've seen this crossword clue in The Times
Q
U
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A

Buddy explains!

The straight part
We know that "Fast Sunday" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fast sunday = quadragesima.
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.

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