The most common and most likely answer to this crossword clue is the 7 letter word BAPTIST
I've seen this crossword clue in The Guardian
B
A
P
T
I
S
T
More clues leading to the result BAPTIST
- Sectarian bishop first to drink a pint
- Bishop past it, woolly sort of Christian
- One who believes in a good soaking
- She’s thoroughly steeped in her faith
- A certain John given bread is tucking in time and time again
- Naughty bits apt to make one religious
- One advocating dunking bread is limited by having no drink
Buddy explains!

The straight part
We know that "one religious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one religious = baptist.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 BAPTIST mean?
BAPTIST noun- A person who baptizes