New anorak covers good old jumper? (8)
I believe the answer is:
kangaroo
'jumper?' is the definition.
(thesaurus)
'new anorak covers good old' is the wordplay.
'new' indicates anagramming the letters.
'covers' means one lot of letters goes inside another.
'good' becomes 'g' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'anorak' with letters rearranged gives 'kanaro'.
'kanaro' enclosing 'g' is 'kangaro'.
'kangaro'+'o'='KANGAROO'
(Other definitions for kangaroo that I've seen before include "Marsupial from down-under" , "Leaping marsupial" , "Jumping marsupial" , "Marsupial that boxes" , "Native marsupial Down Under" .)