Sales talk enthrals everybody in supermarket — bishop may deliver it (8,6)

I believe the answer is:

pastoral letter

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'bishop may deliver it' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'sales talk enthrals everybody in supermarket' is the wordplay.
'sales talk' becomes 'patter' (sales patter).
'enthrals' is an insertion indicator.
'everybody' becomes 'all' (all people).
'in' means one lot of letters goes inside another.
'supermarket' becomes 'store' (I've seen this before).
'all' placed into 'store' is 'storalle'.
'patter' enclosing 'storalle' is 'PASTORAL LETTER'.

Can you help me to learn more?

(Another definition for pastoral letter that I've seen is " ecclesiastical post".)

I've seen this clue in The Times.

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