The most common and most likely answer to this crossword clue is the 8 letter word CROWNING
I've seen this crossword clue in The Daily Telegraph
C
R
O
W
N
I
N
G
More clues leading to the result CROWNING
Buddy explains!

The straight part
We know that "coronation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coronation = crowning.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 CROWNING mean?
CROWNING verb- To place a crown on the head of.
- To formally declare (someone) a king, queen, emperor, etc.
- To bestow something upon as a mark of honour, dignity, or recompense; to adorn; to dignify.
- To form the topmost or finishing part of; to complete; to consummate; to perfect.
- To declare (someone) a winner.
- Of a baby, during the birthing process; for the surface of the baby's head to appear in the vaginal opening.
- To cause to round upward; to make anything higher at the middle than at the edges, such as the face of a machine pulley.
- To hit on the head.
- To shoot an opponent in the back of the head with a shotgun in a first-person shooter video game.
- In checkers, to stack two checkers to indicate that the piece has become a king.
- To widen the opening of the barrel.
- To effect a lodgment upon, as upon the crest of the glacis, or the summit of the breach.
- To lay the ends of the strands of (a knot) over and under each other.
- Supreme; of a surpassing quality or quantity.
- A coronation.
- The act of one who crowns (in various senses).