The most common and most likely answer to this crossword clue is the 7 letter word TRIPOLI
T
R
I
P
O
L
I
More clues leading to the result TRIPOLI
- Run out crude oil here?
- Fresh oil needed on journey in African capital
- Capital tour to west of oil-rig, oddly
- Experience high oil supply from this city?
- Capital made by Republican taking hint about oil supply
- City‘s stumble over refined oil
- Capital with power to stop small group initially living independently
- Capital error over centre of Catholicism
- Stumble on oil surprisingly in kieselguhr
- Oil wasted on voyage to get to port city
Buddy explains!

The straight part
We know that "African capital" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case african capital = tripoli.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 TRIPOLI mean?
TRIPOLI noun- A sedimentary rock composed of the shells of diatoms etc., used for polishing.