The most common and most likely answer to this crossword clue is the 4 letter word SION
I've seen this crossword clue in The Daily Telegraph
S
I
O
N
More clues leading to the result SION
Buddy explains!

The straight part
We know that "holy place" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case holy place = sion.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 SION mean?
SION noun- A descendant, especially a first-generation descendant of a distinguished family.
- The heir to a throne.
- A guardian.
- A detached shoot or twig containing buds from a woody plant, used in grafting; a shoot or twig in a general sense.