The most common and most likely answer to this crossword clue is the 8 letter word PREMISED
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Buddy explains!
The straight part
We know that "mentioned before/ (8)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mentioned before/ (8) = premised.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 PREMISED mean?
PREMISED verb- To state or assume something as a proposition to an argument.
- To make a premise.
- To set forth beforehand, or as introductory to the main subject; to offer previously, as something to explain or aid in understanding what follows.
- To send before the time, or beforehand; hence, to cause to be before something else; to employ previously.
- Having a (specified) premise