The most common and most likely answer to this crossword clue is the 4 letter word ROOS
I've seen this crossword clue in Independent
R
O
O
S
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The straight part
We know that "jumpers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jumpers = roos.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 ROOS mean?
ROOS noun- A member of the Macropodidae family of large marsupials with strong hind legs for hopping, native to Australia.
- A hooded jacket with a front pocket, usually of fleece material, a kangaroo jacket.