The most common and most likely answer to this crossword clue is the 7 letter word MUSTERS
I've seen this crossword clue in The Daily Telegraph
M
U
S
T
E
R
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 = musters.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 MUSTERS mean?
MUSTERS noun- A person of one-eighth African ancestry.
- Gathering.
- Showing.
- To show, exhibit.
- To be gathered together for parade, inspection, exercise, or the like (especially of a military force); to come together as parts of a force or body.
- To collect, call or assemble together, such as troops or a group for inspection, orders, display etc.
- To enroll (into service).
- To gather or round up livestock.