Bar girl has nothing on (6)
I believe the answer is:
saloon
'bar' is the definition.
(I know that saloon is a type of bar)
'girl has nothing on' is the wordplay.
'girl' becomes 'sal' (feminine given name).
'has' means one lot of letters go next to another.
'nothing' becomes 'O' (O resembles 0).
'sal'+'o'+'on'='SALOON'
(Other definitions for saloon that I've seen before include "US bar - type of car" , "Lounge bar" , "Car with separate boot" , "Large public room" , "Pub room" .)