The most common and most likely answer to this crossword clue is the 7 letter word PAPERED
I've seen this crossword clue in Financial Times
P
A
P
E
R
E
D
More clues leading to the result PAPERED
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 = papered.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 PAPERED mean?
PAPERED verb- To apply paper to.
- To document; to memorialize.
- To fill (a theatre or other paid event) with complimentary seats.
- To submit official papers to (a law court, etc.).
- To give public notice (typically by displaying posters) that a person is wanted by the police or other authority.
- To sandpaper.
- To enfold in paper.
- To paste the endpapers and flyleaves at the beginning and end of a book before fitting it into its covers.