The most common and most likely answer to this crossword clue is the 6 letter word ADORNS
A
D
O
R
N
S
Buddy explains!

The straight part
We know that "Decks" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decks = adorns.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 ADORNS mean?
ADORNS verb- To make more beautiful and attractive; to decorate.