Prune-to-be (4)
I believe the answer is:
plum
'prune-to-be' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for plum that I've seen before include "murderer" , "Juicy fruit" , "Shade" , "Fruit < that's highly desirable" , "Edible oval fruit" .)