The most common and most likely answer to this crossword clue is the 7 letter word RAMPION
I've seen this crossword clue in The Daily Telegraph
R
A
M
P
I
O
N
More clues leading to the result RAMPION
Buddy explains!
The straight part
We know that "Plant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plant = rampion.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 RAMPION mean?
RAMPION noun- A species of bellflower with roots and leaves formerly used in salads, Campanula rapunculus
- Any of several flowering plants of the genus Phyteuma, within the family Campanulaceae.