Source of wisdom (6)
I believe the answer is:
oracle
'source of wisdom' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for oracle that I've seen before include "One believed to give divinely-inspired answers" , "Holy place in ancient times where gods prophesied" , "Diviner of the future" , "Holy place where a god was believed to give advice and prophecy" , "Soothsayer" .)