The most common and most likely answer to this crossword clue is the 10 letter word PROSPERITY
I've seen this crossword clue in The Guardian
P
R
O
S
P
E
R
I
T
Y
Buddy explains!
The straight part
We know that "riches?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case riches? = prosperity.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 PROSPERITY mean?
PROSPERITY noun- The condition of being prosperous, of having good fortune