The most common and most likely answer to this crossword clue is the 4 letter word NONE
N
O
N
E
More clues leading to the result NONE
- Not even one sister on the radio
- Not any composition left unfinished!
- Not even one announcer appears regularly
- Hour of prayer held by canon everyday
- Sister’s outspoken; not at all!
- Zero is new factor for all primes
- Not any old name in north-east
- By no means religious, from what we hear
- Hour of prayer for nobody
- Nothing the French said no to Cardinal
Buddy explains!

The straight part
We know that "Zero" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case zero = none.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 NONE mean?
NONE noun- A person without religious affiliation.
- To no extent, in no way.
- Not at all, not very.
- No, not.
- Not any of a given number or group.
- Those without any religious affiliation: atheists and others outside any organized religion.
- A light meal usually eaten around midday, notably when not as main meal of the day.
- A break in play between the first and second sessions.
- (Minnesota) Any small meal, especially one eaten at a social gathering.
- The middle of the afternoon, normally between 2 and 4 pm.
- (often capitalized) The notional first-quarter day of a Roman month, occurring on the 7th day of the four original 31-day months (March, May, Quintilis or July, and October) and on the 5th day of all other months.
- (sometimes capitalized) The ninth hour after dawn (about 3 pm).
- The divine office appointed to the hour.
- The ninth hour of the day counted from sunrise; around three o'clock in the afternoon.
- Time of day when the sun is in its zenith; twelve o'clock in the day, midday.
- The corresponding time in the middle of the night; midnight.
- The highest point; culmination.
- The letter ن in the Arabic script.