Delivery option that might make Don's cap cost less (6-5,4)

I believe the answer is:

second-class post

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'delivery option that' is the definition.
I know nothing about this answer so I can't judge whether this works.

'make don's cap cost less' is the wordplay.
'make' indicates anagramming the letters.
'dons'+'cap'+'cost'+'less'='donscapcostless'
'donscapcostless' anagrammed gives 'SECOND-CLASS POST'.

'might' is the link.

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I've seen this clue in The Independent.

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