Master takes female, 50, in marriage (7)

I believe the answer is:

marital

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

'master takes female 50' is the wordplay.
'master takes female' becomes 'marita' (I can't justify this - if you can you should give a lot more credence to this answer).
't0' becomes 'l' (Roman numeral).
'marita'+'l'='MARITAL'

Can you help me to learn more?

(Other definitions for marital that I've seen before include "Of a wedding" , "Connubial" , "Of nuptials" , "alliance" , "Relating to union of husband and wife" .)

I've seen this clue in The Guardian and The Globe and Mail.

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