The most common and most likely answer to this crossword clue is the 8 letter word FLOWERED
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More clues leading to the result FLOWERED
Buddy explains!

The straight part
We know that "opened" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case opened = flowered.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 FLOWERED mean?
FLOWERED verb- To put forth blooms.
- To decorate with pictures of flowers.
- To reach a state of full development or achievement.
- To froth; to ferment gently, as new beer.
- To come off as flowers by sublimation.
- (of a plant) That has produced flowers.
- Covered or decorated with flowers, or images of flowers.