The most common and most likely answer to this crossword clue is the 6 letter word PINETA
I've seen this crossword clue in The Times
P
I
N
E
T
A
Buddy explains!
The straight part
We know that "places timber may be sourced from" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case places timber may be sourced from = pineta.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 PINETA mean?
PINETA noun- An arboretum, or part of an arboretum or garden, devoted to growing conifers