The most common and most likely answer to this crossword clue is the 8 letter word BRASILIA
I've seen this crossword clue in The Sunday Telegraph
B
R
A
S
I
L
I
A
More clues leading to the result BRASILIA
- Supporters shortened epic in capital
- Lingerie on hipsin S American city
- Capital alibi contrived to protect prince
- Intimate clothing troubles holding one back in capital
- Blair’s going out on first-class return to acquire foreign capital
- Trouble is rising after bar is ransacked in SA capital
- City supporters having trouble getting back after international
- Capital city in trouble is on the up after support of women
- Capital in trouble is suffering setback after initial support
- Harry is a Libra! Capital!
Buddy explains!
The straight part
We know that "Capital city" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case capital city = brasilia.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.