The most common and most likely answer to this crossword clue is the 8 letter word IMPERIAL
I've seen this crossword clue in The Guardian
I
M
P
E
R
I
A
L
More clues leading to the result IMPERIAL
- Referring to British measures, air mile, pint at first changed ...
- Noble adult at first involved in risk
- Like an empire put in danger, if Attila initially invades it
- Supreme folkloric spirit of the skies with no leader
- August: one month before April, unusually around end of June
- Put at risk, adopting a system of measurement
- Supreme leader of Egypt supports a politician and outrageous liar
- Magnificent tune rising in force
- Risk including a kind of measure
- Threaten to imprison a sovereign
Buddy explains!

The straight part
We know that "August" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case august = imperial.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 IMPERIAL mean?
IMPERIAL noun- A bottle of wine (usually Bordeaux) containing 6 liters of fluid, eight times the volume of a standard bottle.
- A writing paper size measuring 30 × 22 inches, or printing paper measuring 32 × 22 inches.
- A card game differing from piquet in some minor details, and in having a trump.
- Any of several combinations of cards which score in this game.
- A crown imperial.
- A tuft of hair on the lower lip (so called from its use by Napoleon III).
- A kind of dome, as in Moorish buildings.
- An outside seat on a diligence.
- A variety of green tea.
- Related to an empire, emperor, or empress.
- Relating to the British imperial system of measurement.
- Very grand or fine.
- Of special, superior, or unusual size or excellence.