Forerunner has some grievances to redress (8)
I believe the answer is:
ancestor
'forerunner' is the definition.
(thesaurus)
'some grievances to redress' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ANCESTOR' can be found hidden inside 'grievances to redress'.
'has' is the link.
(Other definitions for ancestor that I've seen before include "Predecessor" , "Forefather" , "One of one's forebears" , "An escort (anag.)" , "not being of the modern generation" .)