The most common and most likely answer to this crossword clue is the 11 letter word CHAINSTITCH
I've seen this crossword clue in The Times
C
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Buddy explains!
The straight part
We know that "a bit of a jumper?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a bit of a jumper? = chainstitch.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 CHAINSTITCH mean?
CHAINSTITCH noun- An ornamental stitch like the links of a chain, used in crocheting, sewing, and embroidery.
- (machine sewing) A stitch in which the looping of the thread or threads forms a chain on the underside of the work; the loop stitch, as distinguished from the lock stitch.