The most common and most likely answer to this crossword clue is the 9 letter word FORMATION
I've seen this crossword clue in The Daily Telegraph
F
O
R
M
A
T
I
O
N
Buddy explains!
The straight part
We know that "structure" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case structure = formation.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 FORMATION mean?
FORMATION noun- Something possessing structure or form.
- The act of assembling a group or structure.
- The process during which something comes into being and gains its characteristics.
- A rock or face of a mountain.
- A grouping of military units or smaller formations under a command, such as a brigade, division, wing, etc.
- An arrangement of moving troops, ships, or aircraft, such as a wedge, line abreast, or echelon. Often "in formation".
- An arrangement of players designed to facilitate certain plays.
- The process of influencing or guiding a person to a deeper understanding of a particular vocation.
- A structure made of two categories, two functors from the first to the second category, and a transformation from one of the functors to the other.