The most common and most likely answer to this crossword clue is the 5 plus 4 letter word MARDI GRAS
I've seen this crossword clue in Financial Times
M
A
R
D
I
G
R
A
S
More clues leading to the result MARDI GRAS
- Appreciate sources of Roman activities in Roman God's festival
- Wreck lodgings occupied by artist — it's party time!
- River shown in diagrams disrupted carnival
- Ruin archaeological work at artist’s festival
- Dancing girl nearly stops exotic Madras carnival
- Greatly enjoy artist interrupting planet’s feast day
- Celebration of tolerance spoilt, we hear, by ginger gays regularly being thrown out
- The lead up to fast runs in sporting diagrams
- A diagram’s redesigned for festival
- Complex diagrams covering start of route for carnival
Buddy explains!

The straight part
We know that "festival" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case festival = mardi gras.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.