One proposing to get married in a prominent landmark south of New Orleans initially (9)
I believe the answer is:
nominator
'one proposing to' is the definition.
The definition suggests a singular noun which matches the answer.
'married in a prominent landmark south of new orleans initially' is the wordplay.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'a prominent landmark' becomes 'ator' (I can't explain this - if you can you should give a lot more credence to this answer).
'south of' is a charade indicator (letters next to each other) (in a down clue, some letters go under others).
'initially' indicates taking the first letters.
The first letters of 'new orleans' is 'no'.
'm'+'in'+'ator'='minator'
'minator' put after 'no' is 'NOMINATOR'.
'get' is the link.
Can you help me to learn more?
(Other definitions for nominator that I've seen before include "One proposing candidate" , "The proposer" , "One who puts forward a candidate for election" , "One who proposes" , "someone who makes proposal" .)