End up on motorway leaving a resort on Biscayne Bay (5)
I believe the answer is:
miami
'a resort on biscayne bay' is the definition.
'end up on motorway' is the wordplay.
'end up' becomes 'mia' (I've seen this in other clues).
'on' says to put letters next to each other.
'motorway' becomes 'mi' (resembles M1, English motorway).
'mia'+'mi'='MIAMI'
'leaving' is the link.
(Other definitions for miami that I've seen before include "I put out of action when returning" , "state" , "US city" , "Resort city in SE Florida" , "US town" .)