The most common and most likely answer to this crossword clue is the 6 letter word RICHES
I've seen this crossword clue in The Guardian
R
I
C
H
E
S
More clues leading to the result RICHES
Buddy explains!
The straight part
We know that "Fortune" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fortune = riches.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 RICHES mean?
RICHES noun- Money, goods, wealth, treasure.
- An abundance of anything desirable.