Offer shop might have on crapper loaf regularly (5)

I believe the answer is:

bogof

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'offer shop might have' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'crapper loaf regularly' is the wordplay.
'crapper' becomes 'bog' (I can't explain this - if you can you should give a lot more credence to this answer).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'loaf' are 'of'.
'bog'+'of'='BOGOF'

'on' acts as a link.

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