Decoration for the cake (3)
I believe the answer is:
bar
I believe this is a double definition.
'decoration' is the first definition.
(I know that bar is a type of mark)
'cake' is the second definition.
(synonyms)
'for the' acts as a link.
(Other definitions for bar that I've seen before include "Rigid piece of metal" , "Impediment" , "shoal at mouth of river" , "Pub; restriction" , "an amount of pressure" .)