The most common and most likely answer to this crossword clue is the 9 letter word BURGEONED
B
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G
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More clues leading to the result BURGEONED
Buddy explains!

The straight part
We know that "Rose" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rose = burgeoned.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 BURGEONED mean?
BURGEONED verb- To grow or expand.
- To swell to the point of bursting.
- Of plants, to bloom, bud.