Fundamental racial problem with daughter (7)
I believe the answer is:
radical
'fundamental' is the definition.
(thesaurus)
'racial problem with daughter' is the wordplay.
'problem with' indicates an anagram.
'daughter' becomes 'd'.
'racial' anagrammed with 'd' makes 'RADICAL'.
(Other definitions for radical that I've seen before include "Political extremist" , "Dial car in order to be drastic" , "left-winger" , "Fundamental - thoroughgoing" , "Tending towards extreme political views" .)