It is a rum used for dessert (8)
I believe the answer is:
tiramisu
'dessert' is the definition.
(I know that tiramisu is a type of dessert)
'it is a rum used' is the wordplay.
'used' indicates anagramming the letters.
'it'+'is'+'a'+'rum'='itisarum'
'itisarum' anagrammed gives 'TIRAMISU'.
'for' is the link.
(Other definitions for tiramisu that I've seen before include "Sweet" , "It. dessert, literally pick me up" , "Italian dessert with coffee and liqueur" , "Dessert (Italian "pick me up")" , "Italian dessert of cake, coffee and chocolate" .)