The most common and most likely answer to this crossword clue is the 9 letter word POLYMATHS
I've seen this crossword clue in The Guardian
P
O
L
Y
M
A
T
H
S
More clues leading to the result POLYMATHS
Buddy explains!
The straight part
We know that "All-round experts" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case all-round experts = polymaths.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 POLYMATHS mean?
POLYMATHS noun- A person with extraordinarily broad and comprehensive knowledge.