Oaks-to-be (6)
I believe the answer is:
acorns
'oaks-to-be' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for acorns that I've seen before include "From which 23 down grow" , "nuts" , "Potential oaks?" , "wild fruit" , "Seeds of the oak" .)