Spice Girl is after backing short tune (6)
I believe the answer is:
nutmeg
'spice' is the definition.
(I know that Nutmeg is a type of spice)
'girl is after backing short tune' is the wordplay.
'girl' becomes 'meg' ().
'is after' means one lot of letters go next to another.
'backing' shows that the letters should be reversed in order.
'short' means to remove the last letter.
'tune' with its final letter taken off is 'tun'.
'tun' reversed gives 'nut'.
'meg' put after 'nut' is 'NUTMEG'.
(Other definitions for nutmeg that I've seen before include "One grated as spice" , "spicy stuff" , "Hard seed of tropical tree used as spice" , "Variety of spice" , "it's used by bakers" .)