Farewell party visited by Pope, also earlier (6-2)

I believe the answer is:

toodle-oo

But I can't explain it at all!

(Other definitions for toodle-oo that I've seen before include "See you later!" , "Ta-ta" , "Farewell (old inf.)" , "Bye-bye!" , "Bye!" .)

I've seen this clue in The Times.

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