The most common and most likely answer to this crossword clue is the 13 letter word CHRYSANTHEMUM
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More clues leading to the result CHRYSANTHEMUM
Buddy explains!

The straight part
We know that "Perennial" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case perennial = chrysanthemum.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 CHRYSANTHEMUM mean?
CHRYSANTHEMUM noun- Any of many flowering perennial plants, of the genus Chrysanthemum, native to China, that have showy radiate heads.