The most common and most likely answer to this crossword clue is the 8 letter word ENRICHED
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More clues leading to the result ENRICHED
Buddy explains!

The straight part
We know that "Improved" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case improved = enriched.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 ENRICHED mean?
ENRICHED verb- To enhance.
- To make (someone or something) rich or richer.
- To adorn, ornate more richly.
- To add nutrients or fertilizer to the soil; to fertilize.
- To increase the amount of one isotope in a mixture of isotopes, especially in a nuclear fuel.
- To add nutrients to foodstuffs; to fortify
- To make to rise the proportion of a given constituent.
- To add new elements, to complete.