Lucky dip bishop organised, backing nevertheless also required (4,3)

I believe the answer is:

bran tub

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'lucky dip' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for bran tub that I've seen before include "Gifts from here" , "Lucky-dip container" , "place for a dip" , "Container for lucky dip" .)

I've seen this clue in The Times.

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