Highly cultivated plant? (6)
I believe the answer is:
alpine
'highly cultivated' is the definition.
The answer and definition are not the same part of speech. However, adjectives and past participle verbs can sometimes mean the same thing.
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for alpine that I've seen before include "from Germany, Austria etc" , "seen in rocky state?" , "Native growing up in mountainous area" , "Relating to high mountains" , "Plant of high mountains" .)