The most common and most likely answer to this crossword clue is the 6 plus 5 letter word SPRING ONION
I've seen this crossword clue in The Times
S
P
R
I
N
G
O
N
I
O
N
More clues leading to the result SPRING ONION
- Bulbous item — suddenly reveal one held between legs
- Salad plant to reveal unexpectedly to big cat, first off
- A vegetable? Well no, one certainly not to be pulled up
- Vegetable: bound to get on repeatedly planting one
- Make known suddenly backing for top salad ingredient
- Well advanced, one’s old — not primarily a candidate for ‘salad days’?
Buddy explains!
The straight part
We know that "A vegetable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a vegetable = spring onion.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.