The most common and most likely answer to this crossword clue is the 9 letter word DEVELOPER
I've seen this crossword clue in Financial Times
D
E
V
E
L
O
P
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Buddy explains!
The straight part
We know that "One in property" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one in property = developer.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 DEVELOPER mean?
DEVELOPER noun- A person or entity engaged in the creation or improvement of certain classes of products.
- A real estate developer; a person or company who prepares a parcel of land for sale, or creates structures on that land.
- A film developer; a person who uses chemicals to create photographs from photograph negatives.
- A liquid used in the chemical processing of traditional photos.
- (dyeing) A reagent used to produce an ingrain color by its action upon some substance on the fiber.
- A software developer; a person or company who creates or modifies computer software.