The most common and most likely answer to this crossword clue is the 8 plus 2 letter word STRAIGHT UP
I've seen this crossword clue in The Guardian
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More clues leading to the result STRAIGHT UP
Buddy explains!
The straight part
We know that "Shortest way to the top/believe me" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shortest way to the top/believe me = straight up.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 STRAIGHT UP mean?
STRAIGHT UP adjective- Authentic, serious