Due west, iceboat’s prow to damage US port (5)
I believe the answer is:
miami
'port' is the definition.
(I've seen this before)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for miami that I've seen before include "place associated with vice?" , "I put out of action when returning" , "tourist centre" , "Florida resort city, Beach" , "US city" .)