The most common and most likely answer to this crossword clue is the 9 letter word TRIALISTS
I've seen this crossword clue in The Guardian
T
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Buddy explains!
The straight part
We know that "who hope to become major players" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case who hope to become major players = trialists.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 TRIALISTS mean?
TRIALISTS noun- An advocate of trialism, especially with reference to the proposed creation of a state comprising Austria, Hungary, and a Slavic region.
- A person who takes part in a trial (of a drug etc.)