Upsetting argument with family over Gold Coast girls in these socio-economic groups (7,7)

I believe the answer is:

working classes

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'upsetting argument with family over gold coast girls' is the definition.
I can't tell whether this definition defines the answer.

'these socio-economic groups' is the wordplay.
'these socio-economic' becomes 'working' (I can't explain this - if you can you should believe this answer much more).
'groups' becomes 'classes' (class is a kind of group).
'working'+'classes'='WORKING CLASSES'

'in' is the link.

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I've seen this clue in the Sydney Morning Herald.

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