The most common and most likely answer to this crossword clue is the 8 letter word SYCAMORE
I've seen this crossword clue in The Guardian
S
Y
C
A
M
O
R
E
More clues leading to the result SYCAMORE
- Tree on borders of Surrey appeared full of gold
- So my care is to propagate a tree
- Yankee eccentric in burning American plane
- Tree rose may spread over one side of cottage
- Ill-sounding Italian’s love for maple
- Love collecting first of caterpillars in spring after climbing tree
- Tree not doing so well, increasing numbers said
- Tips for safety connected with worry about second tree
- Growth of many branches as US retailer backs Scandinavian currency
- Simon came across yellow plane in US
Buddy explains!

The straight part
We know that "tree" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tree = sycamore.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 SYCAMORE mean?
SYCAMORE noun- Any of several North American plane trees, of the genus Platanus, especially Platanus occidentalis (American sycamore).
- A large British and European species of maple, Acer pseudoplatanus, known in North America as the sycamore maple.
- A large tree bearing edible fruit, Ficus sycomorus, allied to the common fig and found in Egypt and Syria; also called the sycamore fig or the fig-mulberry; the Biblical sycomore.