"Stay out of combat" is an optional mission objective in Sequence 3 / Memory 05: Sugarcane and its Yields
What's different this time from similar objectives earlier in the game, is that now it includes naval combat. You need to avoid being spotted by enemy ships
The field of vision of other ships is represented by a yellow cone. Try to avoid those cones altogether, but if you do land inside one of them, just raise speed to full sails and sail out of the code quickly, before it turns to red.
