Fruits of the oak (6)
I believe the answer is:
acorns
'fruits of the oak' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for acorns that I've seen before include "nuts" , "Potential oaks?" , "'From little . . . . . . mighty oaks do grow'" , "'Great oaks from little ...... grow'" , "From which great oak trees grow" .)