Marine personnel reported for sea trip (6)
I believe the answer is:
cruise
'sea trip' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for cruise that I've seen before include "Holiday on liner" , "Shipboard holiday" , "Ship holiday" , "Sail on a ship" , "Sea trip" .)