Jumper let out for grub (6)
I believe the answer is:
rootle
'grub' is the definition.
(I've seen this before)
'jumper let out' is the wordplay.
'jumper' becomes 'roo' (short for kangaroo, something which jumps).
'out' is an anagram indicator (out can mean wrong or inaccurate).
'let' is an anagram of 'tle'.
'roo'+'tle'='ROOTLE'
'for' acts as a link.
(Other definitions for rootle that I've seen before include "grub" , "Dig (as pig for truffles)" , "Search the ground as pigs do" , "Dig with snout" .)