Film of father with girl (6)
I believe the answer is:
patina
'film' is the definition.
(both can mean a layer)
'father with girl' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'with' says to put letters next to each other.
'girl' becomes 'tina' (girl's name).
'pa'+'tina'='PATINA'
'of' is the link.
(Other definitions for patina that I've seen before include "Sheen acquired from constant handling" , "Film forming on bronze" , "well-worn surface" , "Surface shine" , "Fine coating on surface" .)