Pop legend Gary, not entirely drunk, seeing apparition (12)

I believe the answer is:

doppelganger

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'apparition' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'pop legend gary not entirely drunk' is the wordplay.
'not entirely' means to remove the last letter (most but not all of the word).
'drunk' is an anagram indicator.
'pop'+'legend'+'gary'='poplegendgary'
'poplegendgary' with its last letter taken away is 'poplegendgar'.
'poplegendgar' with letters rearranged gives 'DOPPELGANGER'.

'seeing' acts as a link.

Can you help me to learn more?

(Other definitions for doppelganger that I've seen before include "Living person's double" , "Ghostly double of a living person - green Lapp god (anag)" , "Spirit double" , "Ghostly double that haunts its living counterpart" , "A person's spitting image" .)

I've seen this clue in The Telegraph.

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