One in a hole, at golf? (3)

I believe the answer is:

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'a hole at golf?' is the definition.
I can't judge whether this definition defines the answer.

'one in' is the wordplay.
'one' becomes 'p' (I can't explain this - if you can you should give a lot more credence to this answer).
'p'+'in'='PIN'

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(Other definitions for pin that I've seen before include "Initially, confidential number for use of bank card" , "Badge" , "Fixing device" , "Sewer's aid" , "Fastener; skittle" .)

I've seen this clue in the Evening Standard.

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