The most common and most likely answer to this crossword clue is the 9 letter word BASILICAN
I've seen this crossword clue in Independent
B
A
S
I
L
I
C
A
N
More clues leading to the result BASILICAN
- White powder pocketed by outlaw from a Christian church
- Shinto leader in state of release with positive affirmation of the church
- Expression of one’s self-confidence after saint appears in big church
- Outlaw cases compound
- Coming from church, what might Rosemary say confidently to Herb?
- Quartz, perhaps, used in bar of a magnificent Roman building
Buddy explains!
The straight part
We know that "in big church" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in big church = basilican.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.