The most common and most likely answer to this crossword clue is the 9 letter word FURNISHED
I've seen this crossword clue in The Times
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More clues leading to the result FURNISHED
Buddy explains!

The straight part
We know that "supplied" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supplied = furnished.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 FURNISHED mean?
FURNISHED verb- To provide a place with furniture, or other equipment.
- To supply or give (something).
- To supply (somebody) with something.
- Equipped with whatever is needed
- Supplied with furniture