The most common and most likely answer to this crossword clue is the 4 plus 2 plus 3 plus 6 letter word LILY OF THE VALLEY
I've seen this crossword clue in The Times
L
I
L
Y
O
F
T
H
E
V
A
L
L
E
Y
More clues leading to the result LILY OF THE VALLEY
Buddy explains!
The straight part
We know that "Dean's flower lady" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dean's flower lady = lily of the valley.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.