The most common and most likely answer to this crossword clue is the 10 letter word GABERDINES
I've seen this crossword clue in The Daily Telegraph
G
A
B
E
R
D
I
N
E
S
More clues leading to the result GABERDINES
Buddy explains!

The straight part
We know that "coats" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coats = gaberdines.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 GABERDINES mean?
GABERDINES noun- A long cloak.
- A textile: gabardine.