Jumper made from calf leather (4)
I believe the answer is:
flea
'jumper' is the definition.
(something that jumps)
'from calf leather' is the wordplay.
'from' says the answer is hidden in the clue.
'FLEA' is hidden in the letters of 'calf leather'.
'made' is the link.
(Other definitions for flea that I've seen before include "In your ear, this insect is a rebuke" , "Insect (which you don't want in your ear!)" , "Jumping, biting insect" , "Jumping parasite" , "Bloodsucking parasite" .)