There are ten definitions below. The answer to each of the definitions from two onwards is an anagram of the previous answer with one letter added. So SPOT could be followed by POSIT; that is, SPOT + I rearranged.
1. The perpendicular pronoun
2. The ratio of a circle's circumference to its diameter
3. Nickname of former Speaker of the House Thomas P. O'Neill
4. A narrow piece of land formed by longshore drift
5. Walks or runs with quick light steps
6. Alternative term for handwriting
7. Muscle having three points of attachment
8. An archaic word for Recipes
9. The most spine-chilling
10. Central points of earthquakes
Pleasingly each successive answer starts with a different letter, and is a "proper" anagram of the previous answer.