Assuming that’s what the green is for (7,2)

I believe the answer is:

putting on

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'assuming that's what' is the definition.
I can't tell whether this definition defines the answer.

'green is for' is the wordplay.
'green' becomes 'putting green' (synonyms).
'is for' becomes 'on' (I can't explain this - if you can you should give a lot more credence to this answer).
'putting'+'on'='PUTTING ON'

'the' is the link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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