Fruit with wrinkled skin (4)
I believe the answer is:
ugli
'fruit with wrinkled skin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ugli that I've seen before include "Jamaican form of 6" , "Grapefruit/tangerine hybrid" , "Trademark name for a hybrid citrus fruit" , "Citrus fruit of the West Indies" , "Trademarked hybrid citrus fruit" .)