The most common and most likely answer to this crossword clue is the 8 letter word WISTARIA
I've seen this crossword clue in The Times
W
I
S
T
A
R
I
A
More clues leading to the result WISTARIA
Buddy explains!

The straight part
We know that "a bloomer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a bloomer = wistaria.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 WISTARIA mean?
WISTARIA noun- Any of several woody climbing vines, of the genus Wisteria, native to the East Asian countries of China, Korea, and Japan and the eastern United States.