The most common and most likely answer to this crossword clue is the 9 letter word CLAPBOARD
I've seen this crossword clue in The Times
C
L
A
P
B
O
A
R
D
More clues leading to the result CLAPBOARD
Buddy explains!

The straight part
We know that "timber" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case timber = clapboard.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 CLAPBOARD mean?
CLAPBOARD noun- A narrow board, usually thicker at one edge than the other, used as siding for houses and similar structures of frame construction.
- Such boards, arranged horizontally and overlapping with thick edge down, collectively, as siding.
- An oak board of a size used for barrel staves.
- To cover with clapboards.
- A clapper board; a device used in film production, having hinged boards that are brought together with a clap, used to synchronize picture and sound at the start of each take of a motion picture or other video production.