The most common and most likely answer to this crossword clue is the 5 letter word AMASS
A
M
A
S
S
More clues leading to the result AMASS
- Collect in a church service
- Accumulate degrees, when travelling around
- Collect is a church form of worship
- Stockpile a lot of documents head of army sent in
- Gather tea's brought up in the morning
- A mother with two sons to collect
- Pile up in a state
- Assemble team as security guards
- Source of antiquated writings stocks a hoard
- Collect fool's confession
Buddy explains!

The straight part
We know that "A communion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a communion = amass.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 AMASS mean?
AMASS noun- A large number of things collected or piled together.
- The act of amassing.
- To collect into a mass or heap.
- To gather a great quantity of; to accumulate.