Master takes female, 50, in marriage (7)
I believe the answer is:
marital
'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" .)