The most common and most likely answer to this crossword clue is the 7 letter word APOSTLE
I've seen this crossword clue in The Daily Telegraph
A
P
O
S
T
L
E
More clues leading to the result APOSTLE
- Champion bitter about job
- One sent out letters covered in beer
- Champion beer seen outside station
- Supporter lost ground in a sport
- Bartholomew, perhaps, bitter about job
- Messenger's job secured by porter
- Christian missionary throwing stone into a bar
- Bitter about letters, supporter of cause
- Missionary has job cutting beer
- Column penned by perhaps bitter advocate
Buddy explains!

The straight part
We know that "Early Christian" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case early christian = apostle.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 APOSTLE mean?
APOSTLE noun- A missionary, or leader of a religious mission, especially one in the early Christian Church (but see Apostle).
- A pioneer or early advocate of a particular cause, prophet of a belief.
- A top-ranking ecclesiastical official in the twelve seat administrative council of The Church of Jesus Christ of Latter-day Saints.
- A person who is plucked, that is, refused an academic degree.
- A letter dismissory.
- A note sent to an appeals court presenting the appeal in summary.
- The trial court record sent to an appeal court concerning an appeal.