The most common and most likely answer to this crossword clue is the 6 letter word ACACIA
I've seen this crossword clue in The Daily Telegraph
A
C
A
C
I
A
More clues leading to the result ACACIA
- About to go back to a security organisation - one with several branches
- Tree initially as charming as collection in arboretum
- Regularly obscuring fancy arch is a flowering plant
- Plant account penned by American spies
- Plant in America around spies
- American agents about to be hiding in tree?
- Caught a group of spies sitting under a tree
- Shrub in areas full of prickly plants, with temperature dropping
- 3A’s cross-country international, initially, rerranged on a cold continent, reportedly
- Twice Bill and I get together in a gum tree
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 ACACIA mean?
ACACIA noun- A shrub or tree of the tribe Acacieae.
- The thickened or dried juice of several species in Acacieae, in particular Vachellia nilotica (syn. Acacia nilotica), the Egyptian acacia.
- A false acacia; robinia tree, Robinia pseudoacacia.
- Gum arabic; gum acacia.
- Any of several related trees, such as the locust tree.
- A light to moderate greenish yellow with a hint of red.
- (history) A roll or bag, filled with dust, borne by Byzantine emperors, as a memento of mortality. It is represented on medals.