The most common and most likely answer to this crossword clue is the 8 letter word CLEMATIS
I've seen this crossword clue in The Daily Telegraph
C
L
E
M
A
T
I
S
More clues leading to the result CLEMATIS
- . Colourful plant found in Sweden after climate changed
- Climate’s bad for one sort of plant
- Climate changes beginning to startle climber
- Climate changes beginning to stunt old man’s beard
- Climber‘s claim set to collapse
- Is after cold meal served on time
- Lime and cats affected plant
- One climbs over it — a member of 12 second
- St Michael sadly missing opening of his flower
- Plant in changing climate succeeded
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 = clematis.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 CLEMATIS mean?
CLEMATIS noun- Any plant of the genus Clematis, vigorous climbing lianas found throughout the temperate zones.