Good weather, but could it mean a thin time? (4,3)

I believe the answer is:

fine day

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'good weather but could it mean a' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'thin time?' is the wordplay.
'thin' becomes 'fine' (similar in meaning).
'time?' becomes 'day' (day is a kind of time).
'fine'+'day'='FINE DAY'

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I've seen this clue in the Evening Standard.

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