Possible Clues:

• Person on board?
• Board-riding, breeze-assisted sportsperson
• With US friend adrift on river, someone riding across the water
• One stands, taking position on board, prepared for any blow
• Turn skiff, finally overwhelmed by more confident person on board
• One who might wipe out victory refused somehow having eradicated base on river
• Board-and-sail sportsperson
• Making progress on the board takes a blow
• One who looks forward to getting on to the board?
• Board sailor