I end up getting married in large US resort (5)
I believe the answer is:
miami
'us resort' is the definition.
(resort in Florida)
'i end up getting married' is the wordplay.
'end' becomes 'aim' (both can mean a purpose or goal).
'up' is a reversal indicator (in down clue: letters go upwards).
'getting' indicates putting letters inside.
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'i'+'aim'='iaim'
'iaim' backwards is 'miai'.
'miai' placed around 'm' is 'MIAMI'.
'in large' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for miami that I've seen before include "Popular sun-city of Florida" , "Port in Florida" , "Prejudice in favour of one person or thing" , "Floridian city" , "Sunshine city in SE Florida" .)