The term 'CERTAIN BOXER' can be broken down into two crossword solutions: WELTER (6 letters) and DOG (3 letters). A welterweight boxer is a professional boxer who weighs between 140 and 147 pounds. The term 'DOG' is often used to refer to a boxer who has been in the ring for too long and is past his prime. Therefore, the term 'CERTAIN BOXER' could refer to a welterweight boxer who is still in his prime and has not been in the ring for too long.