The most common and most likely answer to this crossword clue is the 10 letter word DESHABILLE
I've seen this crossword clue in The Daily Telegraph
D
E
S
H
A
B
I
L
L
E
Buddy explains!
The straight part
We know that "state of undress" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case state of undress = deshabille.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 DESHABILLE mean?
DESHABILLE noun- The state of being partially clothed
- A garment worn when one is in a state of undress; a négligée