Crossword Genius

Unfermented juice below requirements? It's inevitable (5,4)

Ross

I believe the answer is:

needs must

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

'unfermented juice below requirements? it's' is the wordplay.
'unfermented juice' becomes 'mus' (I can't justify this - if you can you should believe this answer much more).
'below' means one lot of letters go next to another (in a down clue, some letters go below others).
'requirements?' becomes 'needs' ('need' can be a synonym of 'requirement').
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'mus' after 'needs' is 'needsmus'.
'needsmus'+'t'='NEEDS MUST'

Can you help me to learn more?

(Other definitions for needs must that I've seen before include "It's inevitable" , "It is necessary" , "'. . . . . . . . . when the devil drives'" , "there's no alternative" , "what wine-making does" .)

I've seen this clue in The Times.
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