Cryptic crossword clue
Repetition unknown, having tightened up old journal earlier 9

The most common and most likely answer to this crossword clue is the 9 letter word TAUTOLOGY

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Buddy explains!

The straight part
We know that "Repetition" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case repetition = tautology.
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 TAUTOLOGY mean?

TAUTOLOGY noun
  1. Redundant use of words, a pleonasm, an unnecessary and tedious repetition.
  2. An expression that features tautology.
  3. In propositional logic: a statement that is true for all truth values of its propositional variables. In first-order logic: a statement that is true for all truth values of its Boolean atoms.

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