Beat can have several uses in the Hornblower universe.
Beating or striking someone.
Winning in a game of cards or other games or sports. 'Hornblower beat his opponents at Whist.
Beat to Quarters, preparing the ship and crew for battle.
Beating, running close-hauled, working to a destination upwind by tacking or wearing. If the destination is Portsmouth and the wind is from up-channel, sailing alternately on the port and starboard tacks, switching by tacking or by wearing the ship (jibing).
Beating at Wikipedia.