Girl's fabrication protecting fool (6)
I believe the answer is:
lassie
'girl's' is the definition.
(lassie is a kind of girl)
'fabrication protecting fool' is the wordplay.
'fabrication' becomes 'lie' (a lie is an invention or fabrication).
'protecting' is an insertion indicator (inserted letters are held or protected).
'fool' becomes 'ass' (both can mean a stupid person).
'lie' placed around 'ass' is 'LASSIE'.
(Other definitions for lassie that I've seen before include "Film and TV dog" , "Cinema dog who went home" , "Young Scottish girl or Hollywood lost dog" , "Girl from Scotland and dog from film" , "Movie role for several dog stars" .)