The most common and most likely answer to this crossword clue is the 5 letter word GHOST
G
H
O
S
T
More clues leading to the result GHOST
- Write someone else’s book? That’s the spirit
- Spirit shown by good party organiser
- Good entertainer providing spirit
- Good army haunt
- Good old army spirit
- Grand present sticks in trees
- Suggestion from good master of ceremonies
- Good landlord serves spirit
- Spirit of Van Gogh, ostensibly
- Suggestion of grand crowd …
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 = ghost.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 GHOST mean?
GHOST noun- The spirit; the soul of man.
- The disembodied soul; the soul or spirit of a deceased person; a spirit appearing after death
- Any faint shadowy semblance; an unsubstantial image
- A false image formed in a telescope, camera, or other optical device by reflection from the surfaces of one or more lenses.
- An unwanted image similar to and overlapping or adjacent to the main one on a television screen, caused by the transmitted image being received both directly and via reflection.
- A ghostwriter.
- An unresponsive user on IRC, resulting from the user's client disconnecting without notifying the server.
- An image of a file or hard disk.
- An understudy.
- A covert (and deniable) agent.
- The faint image that remains after an attempt to remove graffiti.
- An opponent in a racing game that follows a previously recorded route, allowing players to compete against previous best times.
- A dead person whose identity is stolen by another. See ghosting.
- (in names of species) White or pale.
- (in names of species) Transparent or translucent.
- Abandoned.
- Remnant; the remains of a(n).
- Perceived or listed but not real.
- Of cryptid, supernatural or extraterrestrial nature.
- Substitute.
- To haunt; to appear to in the form of an apparition.
- To die; to expire.
- To ghostwrite.
- To sail seemingly without wind.
- To copy a file or hard drive image.
- To gray out (a visual item) to indicate that it is unavailable.
- To forcibly disconnect an IRC user who is using one's reserved nickname.
- To appear without warning; to move quickly and quietly; to slip.
- To kill.
- To break up with someone without warning or explanation; to perform an act of ghosting.