Crossword Genius

Decisive point in wine classification vote (4)

Ross

I believe the answer is:

crux

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'decisive point' is the definition.
(I've seen this before)

'wine classification vote' is the wordplay.
'wine classification' becomes 'cru' (I can't justify this - if you can you should believe this answer much more).
'vote' becomes 'x' (how votes are marked).
'cru'+'x'='CRUX'

'in' is the link.

Can you help me to learn more?

(Other definitions for crux that I've seen before include "Decisive point of an issue" , "Core" , "Nub" , "Essential point of problem, decision etc" , "Most important point at issue" .)

I've seen this clue in The Irish Times.
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