Red giant or white dwarf, say (4)

I believe the answer is:

star

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'red giant or white dwarf' is the definition.
(I've seen this in another clue)

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

Can you help me to learn more?

(Other definitions for star that I've seen before include "Pointed shape" , "Rush" , "- - of Bethlehem" , "Possible Christmas tree topper?" , "top player" .)

I've seen this clue in the Evening Standard.

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