Crossword Genius

Outcome requiring a snap judgement? (5,6)

Ross

I believe the answer is:

photo finish

I'm a little stuck... Click here to teach me more about this clue!

'outcome' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?

'a snap judgement?' is the wordplay.
'a snap' becomes 'photo' (I've seen this before).
'judgement?' becomes 'finish' (I can't explain this - if you can you should give a lot more credence to this answer).
'photo'+'finish'='PHOTO-FINISH'

'requiring' is the link.

Can you help me to learn more?

(Other definitions for photo finish that I've seen before include "Close ending to a race" , "Virtual dead heat in a horse race" .)

I've seen this clue in The Times.
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