Confront Helen, a GLC eccentric (9)
I believe the answer is:
challenge
'confront' is the definition.
(thesaurus)
'helen a glc eccentric' is the wordplay.
'eccentric' is an anagram indicator.
'helen'+'a'+'glc'='helenaglc'
'helenaglc' is an anagram of 'CHALLENGE'.
(Other definitions for challenge that I've seen before include "Object to" , "Issue an invitation to compete" , "Invitation to contest" , "difficult feat" , "Ask to take part in a contest" .)