The most common and most likely answer to this crossword clue is the 4 letter word PIUS
I've seen this crossword clue in The Times
P
I
U
S
More clues leading to the result PIUS
Buddy explains!

The straight part
We know that "Name for religious leader" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case name for religious leader = pius.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.