Fruit, cross between grapefruit and tangerine (4)
I believe the answer is:
ugli
(Other definitions for ugli that I've seen before include "Mottled tangelo hybrid" , "Citrus fruit cross (which sounds offensive!)" , "Cross between Seville orange, grapefruit and tangerine" , "so to speak, for > fruit" , "Unattractive-sounding fruit?" .)