In ancient Thebes, a goddess (4)
I believe the answer is:
Here is my best explanation:
'a goddess' is the definition.
(I've seen this before)
'in ancient thebes' is the subsidiary indication.
'in' says the answer is hidden in the clue.
'hebe' can be found hidden inside 'ancient thebes'.
(Other definitions for hebe that I've seen before include "Be he a plant?", "Wife of Hercules", "Goddess of youth and flowering shrub", "Greek goddess of youth, wife of Hercules", "Plant", "Flowering shrub", "Olympian cupbearer - evergreen garden shrub", "Youth personified", "Shrub - goddess of youth" and "Evergreen shrub".)