Loss of girl’s looks and bearing (13)
I believe the answer is:
disappearance
'loss' is the definition.
(thesaurus)
'girl's looks and bearing' is the wordplay.
'girl's' becomes 'dis'.
'looks and bearing' becomes 'appearance'.
'dis'+'appearance'='DISAPPEARANCE'
'of' is the link.
(Other definitions for disappearance that I've seen before include "Vanishing act" , "Departure from view" , "getaway" , "Act of becoming invisible" , "Exit (maybe into thin air)" .)