Girl changing the guard (8)
I believe the answer is:
daughter
'girl' is the definition.
('daughter' can be a synonym of 'girl')
'changing the guard' is the wordplay.
'changing' is an anagram indicator.
'the'+'guard'='theguard'
'theguard' with letters rearranged gives 'DAUGHTER'.
(Other definitions for daughter that I've seen before include "Relation" , "Dug earth (anag.)" , "'''Don't put your ... on the stage, Mrs Worthington'' (Noel Coward) (8)'" , "Female child" , "Family member" .)