The most common and most likely answer to this crossword clue is the 10 letter word ENRICHMENT
I've seen this crossword clue in The Daily Telegraph
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Buddy explains!
The straight part
We know that "Nuclear process/that makes one wealthy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nuclear process/that makes one wealthy = enrichment.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 ENRICHMENT mean?
ENRICHMENT noun- The act of enriching or something enriched.
- The process of making enriched uranium.
- The addition of sugar to grape juice used to make wine; chaptalization.
- Extracurricular activities for students.