Last of pickers still to grade fruit (4)
I believe the answer is:
sloe
'fruit' is the definition.
(I've seen this before)
'last of pickers still to grade' is the wordplay.
'last of' says to take the final letters.
The final letters of 'pickers still to grade' are 'SLOE'.
(Other definitions for sloe that I've seen before include "Sour blackthorn fruit" , "Wild plum" , "Sour blue-black fruit" , "Thorny bush with plum-like fruit" , "Black fruit" .)