The most common and most likely answer to this crossword clue is the 6 letter word DIWALI
I've seen this crossword clue in The Times
D
I
W
A
L
I
More clues leading to the result DIWALI
- One rule I would have lifted for festival
- One canon I'd recalled for festival
- I act on instinct, turning up for festival
- One rule: Goliath would upset festival
- Women’s group about to open surrealist festival
- One rule I had lifted for religious festival (6
- Feast from Italy with wife in control at first
- Artist receives one at Welsh festival
- I act by instinct towards the west’s festival
- Painter captures current West Indian festival
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 = diwali.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.