Greek goddess of youth (4)
I believe the answer is:
hebe
'greek goddess of youth' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for hebe that I've seen before include "Herculean bride" , "Greek goddess of youth, wife of Hercules" , "Zeus's daughter; shrub" , "Olympian cupbearer - evergreen garden shrub" , "Youth personified" .)