Possible Clues:

• Four units, in 56-Across
• Large navy vessel
• Try for a six perhaps with last bet for the French courier fighting overseas
• Character in The Odyssey returning after the blast destroyed fighting vessel
• Large naval vessel
• Before joint engagements, one fights in the main
• It's four units long in a popular board game (with the game's other pieces hinted at by the circled letters)
• Following hit, let's repair joint in man-of-war
• The USS Maine, for one
• Game phonetically hinted at by this puzzle's starred entries