The most common and most likely answer to this crossword clue is the 7 letter word PARSNIP
I've seen this crossword clue in The Times
P
A
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More clues leading to the result PARSNIP
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 = parsnip.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 PARSNIP mean?
PARSNIP noun- A biennial plant, Pastinaca sativa, related to the carrot.
- The root of the parsnip, when used as a vegetable.