What a prune once was (4)
I believe the answer is:
plum
'what a prune once was' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for plum that I've seen before include "murderer" , "Damson-like fruit" , "Reddish-purple fruit" , "Dark-red fruit" , "Brilliant" .)