At sea? Right! (9)
I believe the answer is:
starboard
This clue might be a double definition.
'at sea?' is the first definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?
'right' is the second definition.
(right side of a ship)
(Other definitions for starboard that I've seen before include "Right side of ship or plane" , "Ship's right side" , "Sailor's right" , "right to 14 [YACHTS]" , "One side of a ship" .)