Changing anorak, go for jumper (8)
I believe the answer is:
kangaroo
'for jumper' is the definition.
(I've seen this before)
'changing anorak go' is the wordplay.
'changing' is an anagram indicator.
'anorak'+'go'='anorakgo'
'anorakgo' anagrammed gives 'KANGAROO'.
(Other definitions for kangaroo that I've seen before include "Marsupial (two friends of 19)" , "Jumper of grey or red" , "Marsupial from down-under" , "Native marsupial Down Under" , "One's jumpy" .)