Sagacity (6)
I believe the answer is:
wisdom
'sagacity' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for wisdom that I've seen before include "Knowledge coupled with good judgement" , "Erudition" , "Ability to make the right use of knowledge" , "Accumulated learning, sagacity" , "` `Experience is the father of ......' '" .)