The most common and most likely answer to this crossword clue is the 9 letter word AUBERGINE
I've seen this crossword clue in The Guardian
A
U
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More clues leading to the result AUBERGINE
- Vegetable gold, black and green, I gathered
- One in green pants after gold, black, purple
- Goldberg with fiancé regularly in 20
- This vegetable is at home in French lodge
- C in French inn, keeping cool
- Tavern getting hold of popular vegetable
- Purple with fresh air and bungee jumping
- Vegetable outstanding soldier keeps in pannier regularly
- Vegetable from Aube region cooked with nothing removed
- Purple and beige urn — a potty
Buddy explains!

The straight part
We know that "in 20" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in 20 = aubergine.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 AUBERGINE mean?
AUBERGINE noun- An Asian plant, Solanum melongena, cultivated for its edible purple, green, or white ovoid fruit
- The fruit of this plant, eaten as a vegetable
- A dark purple colour; eggplant.