The most common and most likely answer to this crossword clue is the 10 letter word FASCINATOR
I've seen this crossword clue in The Sunday Telegraph
F
A
S
C
I
N
A
T
O
R
More clues leading to the result FASCINATOR
Buddy explains!

The straight part
We know that "Decorative accessory" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decorative accessory = fascinator.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 FASCINATOR mean?
FASCINATOR noun- A fascinating person
- A delicate, often frivolous head decoration worn on the hair, primarily by women
- A type of wool or lace headscarf