The term 'Unexpected Advantage' can be broken down into two crossword solutions, 'BONUS' (5 letters) and 'BOON' (4 letters). BONUS is a term used to describe an extra payment or benefit given to someone in addition to their regular wages or salary. A BOON is a special favor, benefit, or advantage granted or bestowed. Therefore, an Unexpected Advantage could refer to a surprise BONUS or unexpected benefit that someone receives.