Heavenly cartoon character (5)

I believe the answer is:

pluto

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'cartoon character' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for pluto that I've seen before include "Long-haul destination" , "Outermost of the main planets" , "It used to be a planet" , "wartime acronym" , "Greek lord of the underworld, and a planet" .)

I've seen this clue in The Globe and Mail and the Evening Standard.

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