The term 'CERTAIN TERRIER' can be broken down into two crossword solutions: SCOTTIE (7 letters) and RATTER (6 letters). The SCOTTIE is a breed of small dog in the terrier family, originating in Scotland. It is a popular breed of dog, known for its loyalty and intelligence. The Ratter is also a type of terrier, but it is a much smaller breed. It is known for its agility and hunting skills, and is often used to hunt rats and other small animals.