A girl to go out with (5)
I believe the answer is:
sally
'out with' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
'a girl to' is the wordplay.
'a girl' becomes 'sal' (feminine given name).
'to' becomes 'ly' (I can't explain this - if you can you should believe this answer much more).
'sal'+'ly'='SALLY'
'go' is the link.
Can you help me to learn more?
(Other definitions for sally that I've seen before include "army" , "one in 3 the 12 30 [DROP the DEAD DONKEY]" , "Witty comment" , "Go out" , "- - Lunn, flat cake" .)