The most common and most likely answer to this crossword clue is the 3 plus 5 plus 2 plus 3 plus 3 plus 2 plus 3 plus 6 letter word THE LIGHT AT THE END OF THE TUNNEL
I've seen this crossword clue in Financial Times
T
H
E
L
I
G
H
T
A
T
T
H
E
E
N
D
O
F
T
H
E
T
U
N
N
E
L
Buddy explains!
The straight part
We know that "a pointer to eventual success" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a pointer to eventual success = the light at the end of the tunnel.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.