At intervals, action seems a viable plan for film buff (6-4)

I believe the answer is:

cinema-goer

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'film buff' is the definition.
I know nothing about this answer so I can't judge whether this works.

'at intervals action seems a viable plan' is the wordplay.
'at intervals' indicates alternate letters (letters are taken at regular intervals).
'viable plan' becomes 'goer' (I can't explain this - if you can you should believe this answer much more).
'action'+'seems'='actionseems'
The alternate letters of 'actionseems' are 'cinem'.
'cinem'+'a'+'goer'='CINEMA-GOER'

'for' is the link.

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I've seen this clue in The Guardian.

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