Cryptic crossword clue
Notorious gangster's problem casing Yankee plant 7

The most common and most likely answer to this crossword clue is the 7 letter word ALYSSUM

I've seen this crossword clue in The Times
A
L
Y
S
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M

Buddy explains!

The straight part
We know that "plant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plant = alyssum.
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 ALYSSUM mean?

ALYSSUM noun
  1. Any of several plants, of the genus Alyssum, mostly of Eurasian origin, that have racemes of white or yellow flowers.

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