The most common and most likely answer to this crossword clue is the 10 letter word ARROWROOTS
I've seen this crossword clue in The Guardian
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Buddy explains!
The straight part
We know that "white bloomers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case white bloomers = arrowroots.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 ARROWROOTS mean?
ARROWROOTS noun- Maranta arundinacea from the Marantaceae family, a large perennial herb native to the Caribbean area with green leaves about 15 centimeters long.
- Usually preceded by an attributive word: some other plant the rhizomes of which are used to prepare a substance similar to arrowroot (sense 3), such as Zamia integrifolia (Florida arrowroot) or Pueraria montana var. lobata (Japanese arrowroot or kudzu).
- A starchy substance obtained from the rhizomes of an arrowroot plant used as a thickener.