The most common and most likely answer to this crossword clue is the 3 plus 5 plus 2 plus 5 letter word PER ARDUA AD ASTRA
I've seen this crossword clue in The Guardian
P
E
R
A
R
D
U
A
A
D
A
S
T
R
A
Buddy explains!
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.