Trees with acorns (4)
I believe the answer is:
oaks
'trees with acorns' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oaks that I've seen before include "Trees of the genus Quercus" , "Soak up with trees" , "Acorn trees" , "Hardwood trees" , "Epsom Classic race" .)