The most common and most likely answer to this crossword clue is the 7 letter word CASSAVA
I've seen this crossword clue in The Guardian
C
A
S
S
A
V
A
More clues leading to the result CASSAVA
- Tropical plant fool put in wine
- Source of starch fool put in Spanish fizz
- Tropical plant schmuck dipped in wine
- Food and drink consumed by an animal – just the opposite
- Staple food of Africa’s savanna
- Fool’s taken in by wine being a source of starch
- Caught donkey very enthralled by acres of tropical food
- In Cuba a servant nearly sent back starchy food
- It’s starchy dumpling served in wine
- Starch idiot put into sparkling wine
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 = cassava.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 CASSAVA mean?
CASSAVA noun- Manioc (Manihot esculenta), a tropical plant which is the source of tapioca.
- Tapioca, a starchy pulp made with manioc roots.