The most common and most likely answer to this crossword clue is the 6 letter word ROWANS
R
O
W
A
N
S
Buddy explains!
The straight part
We know that "Trees" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trees = rowans.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 ROWANS mean?
ROWANS noun- Sorbus aucuparia, the European rowan.
- Any of various small deciduous trees or shrubs of genus Sorbus, belonging to the rose family, with pinnate leaves, corymbs of white flowers, and usually with orange-red berries.
- A second crop of hay; aftermath.
- A stubble field left unploughed until late in the autumn, so that it can be cropped by cattle.