The most common and most likely answer to this crossword clue is the 6 letter word DIVALI
D
I
V
A
L
I
More clues leading to the result DIVALI
- Four admitted to surrealist festival
- Prima donna left Italy for Hindu festival
- Celebrated singer visits lake before start of Indian religious festival
- Female singer — one supporting large festival
- Singer and boxer linked in religious festival
- Opera singer left Italy for festival
- A livid variety of festival
Buddy explains!

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