The most common and most likely answer to this crossword clue is the 11 letter word CAULIFLOWER
I've seen this crossword clue in The Times
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More clues leading to the result CAULIFLOWER
Buddy explains!

The straight part
We know that "Vegetable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vegetable = cauliflower.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 CAULIFLOWER mean?
CAULIFLOWER noun- Brassica oleracea var. botrytis, an annual variety of cabbage, of which the cluster of young flower stalks and buds is eaten as a vegetable.
- The edible head or curd of a cauliflower plant.
- The swelling of a cauliflower ear.