Seepy spoof rankles shop (3,5)

I believe the answer is:

get smart

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'seepy spoof' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'rankles shop' is the wordplay.
'rankles' becomes 'gets' (I can't justify this - if you can you should believe this answer much more).
'shop' becomes 'mart' (I've seen this in another clue).
'gets'+'mart'='GET SMART'

Can you help me to learn more?

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

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