Fruit that makes dog rave (7)
'fruit' is the definition.
(currant is a kind of fruit)
'dog rave' is the wordplay.
'dog' becomes 'cur' (cur is a kind of dog).
'rave' becomes 'rant' (synonyms).
'that makes' is the link.
(Other definitions for currant that I've seen before include "Product of grape", "Small black raisin", "Something ideal for jamming", "Small dried seedless grape", "Cake ingredient".)