The most common and most likely answer to this crossword clue is the 6 letter word JERKIN
I've seen this crossword clue in The Times
J
E
R
K
I
N
More clues leading to the result JERKIN
- Idiot wearing jacket with sleeves missing
- Yankee at home finds sleeveless jacket
- Idiot wearing jacket
- Schmuck wearing jacket
- Useless person wearing sleeveless jacket
- Clobber clown with it
- Yank wearing old jacket
- Fashionable? Put on donkey jacket!
- Jack, Queen and King in higher end of suit
- Useless person with trendy garment
Buddy explains!

The straight part
We know that "sleeveless jacket" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sleeveless jacket = jerkin.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 JERKIN mean?
JERKIN noun- A type of men's garment popular in the sixteenth and seventeenth centuries: a close-fitting collarless jacket, with or without sleeves.
- A sleeveless jacket, usually leather; a long waistcoat.
- A male gyrfalcon.