The most common and most likely answer to this crossword clue is the 8 letter word PENTAGON
I've seen this crossword clue in Independent
P
E
N
T
A
G
O
N
More clues leading to the result PENTAGON
- The shape of American defence?
- Writer got a new name in regular form
- Figure shut in dock suffering
- Write epithet about military base
- SHAPE military headquarters
- Shape of writing implement with label attached
- . Fold to add shape
- A regular figure in defence of America
- Figure given by Defense Department
- Held back a girl working in military HQ
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 PENTAGON mean?
PENTAGON noun- A polygon with five sides and five angles.
- A fort with five bastions.