The most common and most likely answer to this crossword clue is the 4 plus 4 letter word TREE LINE
I've seen this crossword clue in The Daily Telegraph
T
R
E
E
L
I
N
E
More clues leading to the result TREE LINE
Buddy explains!
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 TREE LINE mean?
TREE LINE noun- The edge of the habitat at which trees are capable of growing; the timberline.