The most common and most likely answer to this crossword clue is the 5 letter word KULAK
I've seen this crossword clue in The Times
K
U
L
A
K
Buddy explains!

The straight part
We know that "rich peasant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rich peasant = kulak.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 KULAK mean?
KULAK noun- A prosperous peasant in the Russian Empire or the Soviet Union, who owned land and could hire workers.