The most common and most likely answer to this crossword clue is the 9 letter word ASCERTAIN
I've seen this crossword clue in The Times
A
S
C
E
R
T
A
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N
More clues leading to the result ASCERTAIN
Buddy explains!

The straight part
We know that "find out" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case find out = ascertain.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 ASCERTAIN mean?
ASCERTAIN verb- To find out definitely; to discover or establish.
- To make (someone) certain or confident about something; to inform.
- To establish, to prove.
- To ensure or effect.