Girl providing cake decoration (8)
I believe the answer is:
angelica
I believe this is a double definition.
'girl' is the first definition.
'cake decoration' is the second definition.
(angelica stalks are used to decorate cakes)
'providing' acts as a link.
(Other definitions for angelica that I've seen before include "Herb" , "Candied part of herbs - nag Alice (anag)" , "Candied leaf-stalks, used to decorate cakes" , "Candied stalks used for cake decoration" , "Candied stalk used in cake decoration" .)