Possible source of Conference’s sparkling repartee (4,4)

I believe the answer is:

pear tree

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But I can't explain it at all! Could you help me understand?

(Other definitions for pear tree that I've seen before include "it should bear fruit" , "What comes with start of Christmas" , "Partridge roost at Christmas?" , "Conference provider" , "present setting" .)

I've seen this clue in The Times.

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