The most common and most likely answer to this crossword clue is the 8 letter word ULTIMATE
U
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More clues leading to the result ULTIMATE
- Best quality regularly associated with one chum
- Last metal: it gets processed after uranium
- Last short epistle used in university, after appropriate period
- Horribly mutilate? That’s extreme
- Team built lead going crazy in final
- Best friend following United ‘til sacked
- Last can be best
- Best meal? But it’s not b___ cooked!
- Perversely mutilate the greatest
- Best lute I am playing with time inside
Buddy explains!

The straight part
We know that "extreme" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extreme = ultimate.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 ULTIMATE mean?
ULTIMATE noun- The most basic or fundamental of a set of things
- The final or most distant point; the conclusion
- The greatest extremity; the maximum
- A non-contact competitive team sport played with a 175 gram flying disc, the object of which is to score points by passing the disc to a player in the opposing end zone; ultimate frisbee.
- To finish; to complete.
- Final; last in a series.
- (of a syllable) Last in a word or other utterance.
- Being the greatest possible; maximum; most extreme.
- Being the most distant or extreme; farthest.
- That will happen at some time; eventual.
- Last in a train of progression or consequences; tended toward by all that precedes; arrived at, as the last result; final.
- Incapable of further analysis; incapable of further division or separation; constituent; elemental.