This is a double definition - the clue gives you two different meanings of the same word, both pointing to the answer.
Look for a word that can mean both 'tremendous' (as in excellent or great) and 'destruction' (as in breaking things). Think about informal ways to describe something as really good, and also consider what happens when things get broken.
Answer: SMASHING | This is a double definition where 'tremendous' means smashing (excellent/great) and 'destruction' also means smashing (breaking things apart).