Going to Pat's house in winter clothes (3,5)

I believe the answer is:

top coats

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

'to pat's house in winter clothes' is the wordplay.
'house' is an insertion indicator.
'in winter clothes' becomes 'co' (I can't explain this - if you can you should give a lot more credence to this answer).
'pats' placed around 'co' is 'pcoats'.
'to'+'pcoats'='TOP-COATS'

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I've seen this clue in the Evening Standard.

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