Marriage means everything to some fiancees! (8)

I believe the answer is:

alliance

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

'everything to some fiancees' is the wordplay.
'everything' becomes 'alli' (I can't explain this - if you can you should believe this answer much more).
'to some' says to take the centre.
The middle letters of 'fiancees' are 'ance'.
'alli'+'ance'='ALLIANCE'

'means' is the link.

Can you help me to learn more?

(Other definitions for alliance that I've seen before include "Combination by treaty" , "Union for mutual benefit" , "The joining by political agreement or treaty" , "Federation" , "Kind of partnership with canaille" .)

I've seen this clue in the Evening Standard.

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