Intelligence possessed by highbrow is dominant (6)
I believe the answer is:
wisdom
'intelligence' is the definition.
(thesaurus)
'possessed by highbrow is dominant' is the wordplay.
'possessed by' says the answer is hidden in the clue.
'WISDOM' is hidden in the letters of 'highbrow is dominant'.
(Other definitions for wisdom that I've seen before include "Learning, knowledge" , "These teeth" , "Accumulated knowledge or enlightenment" , "Accumulated learning, sagacity" , "Property of sage" .)