The most common and most likely answer to this crossword clue is the 8 letter word CONVENES
C
O
N
V
E
N
E
S
Buddy explains!

The straight part
We know that "Gathers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gathers = convenes.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 CONVENES mean?
CONVENES verb- To come together; to meet; to unite.
- To come together, as in one body or for a public purpose; to meet; to assemble.
- To cause to assemble; to call together; to convoke.
- To summon judicially to meet or appear.