A foreigner and about to marry one's mum (7)
I believe the answer is:
swedish
'a foreigner' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'about to marry one's mum' is the wordplay.
'about to' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'marry' becomes 'wed' (synonyms).
'one' becomes 'I' (Roman numeral).
'mum' becomes 'sh' (both are used to tell someone to be quiet).
's'+'wed'+'i'+'sh'='SWEDISH'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for swedish that I've seen before include "Nordic" , "from European country" , "Nationality that swished around" , "Soprano Jenny Lind, b. Stockholm 1798, d. Herefordshire 1887" , "like Bergman" .)