He’s always up to interpolate foreign film (7,8)

I believe the answer is:

eternal optimist

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'he's always up' is the definition.
The definition suggests a singular noun which matches the answer.

'interpolate foreign film' is the wordplay.
'foreign' indicates anagramming the letters (foreign order of the letters).
'film' becomes 'mist' (to film over is to mist or fog over).
'interpolate' is an anagram of 'eternalopti'.
'eternalopti'+'mist'='ETERNAL OPTIMIST'

'to' is the link.

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

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