The most common and most likely answer to this crossword clue is the 8 letter word TATTOOED
I've seen this crossword clue in The Daily Telegraph
T
A
T
T
O
O
E
D
Buddy explains!

The straight part
We know that "Decorated" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decorated = tattooed.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 TATTOOED mean?
TATTOOED verb- To apply a tattoo to (someone or something).
- To hit the ball hard, as if to figuratively leave a tattoo on the ball.
- To tap rhythmically on, to drum.
- Having with one or more tattoos.