The ladies' yen, having to go for one? (5-3)

'one?' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'the ladies' yen having to go' is the wordplay.
'the ladies'' becomes 'loo' ('the ladies' is a type of loo or toilet).
'yen' becomes 'y' (resembles the symbol for the currency of Japan).
'having' means one lot of letters goes inside another.
'to go' becomes 'verb' (I can't explain this - if you can you should give a lot more credence to this answer).
'loo'+'y'='looy'
'looy' placed around 'verb' is 'LOVER-BOY'.

'for' is the link.

Can you help me to learn more?