Show a girl’s fun (7)
I believe the answer is:
display
'show' is the definition.
(display is a kind of show)
'a girl's fun' is the wordplay.
'a girl's' becomes 'dis'.
'fun' becomes 'play' ('play' can be a synonym of 'fun').
'dis'+'play'='DISPLAY'
(Other definitions for display that I've seen before include "Exhibit, show" , "Reveal" , "Showcase" , "Exhibition" , "Demonstrate, show" .)