Starts to experience visitation then séance drifts to fade away (8)

I believe the answer is:

evanesce

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'fade away' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

(Other definitions for evanesce that I've seen before include "Fade away" , "Seen cave (anag) -- disappear gradually" , "Shimmering" , "Fade quickly from sight" .)

I've seen this clue in The Times and The Sunday Times.

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