Cinema OS seen to accept credit (3,6)

I believe the answer is:

big screen

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'cinema' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?

'os seen to accept credit' is the wordplay.
'os' becomes 'big' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to accept' indicates putting letters inside.
'credit' becomes 'cr' (abbreviation).
'seen' placed around 'cr' is 'screen'.
'big'+'screen'='BIG SCREEN'

Can you help me to learn more?

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

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