The most common and most likely answer to this crossword clue is the 6 letter word TILING
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More clues leading to the result TILING
Buddy explains!

The straight part
We know that "Wall decoration" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wall decoration = tiling.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 TILING mean?
TILING verb- To cover with tiles.
- To arrange in a regular pattern, with adjoining edges (applied to tile-like objects, graphics, windows in a computer interface).
- To optimize (a loop in program code) by means of the tiling technique.
- To protect from the intrusion of the uninitiated.
- A covering of tiles.
- The act of applying tiles.
- A tessellation; the covering of a plane with shapes, without overlaps or gaps.
- A technique for optimizing loops by partitioning the iteration space into smaller chunks or blocks that will more easily fit in a cache.