The most common and most likely answer to this crossword clue is the 6 plus 9 letter word GOLDEN PARACHUTE
I've seen this crossword clue in The Guardian
G
O
L
D
E
N
P
A
R
A
C
H
U
T
E
More clues leading to the result GOLDEN PARACHUTE
Buddy explains!
The straight part
We know that "reward at the end" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reward at the end = golden parachute.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.