Guard the disturbed girl (8)
I believe the answer is:
daughter
'girl' is the definition.
('daughter' can be a synonym of 'girl')
'guard the disturbed' is the wordplay.
'disturbed' indicates anagramming the letters.
'guard'+'the'='guardthe'
'guardthe' is an anagram of 'DAUGHTER'.
(Other definitions for daughter that I've seen before include "Family member" , "Female child" , "Family relative" , "Girl" , "Relation" .)