Horse saves one man at sea (8)
I believe the answer is:
maritime
'at sea' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for maritime that I've seen before include "Connected to the sea and sea-faring" , "beside the sea" , "Of seafaring or shipping" , "Relating to the sea" , "Bordering on the sea" .)