### Clue: Is old, old tennis player (about a hundred) descriptive of some figure? (9)
### Answer: ISOSCELES 
 ### Explanation: Definition: descriptive of some figure
 IS + O(abbrev. for "old") + SELES(Monica, former tennis player) **containing**(about) C(Roman numeral for a hundred).
Defn: …, viz. a triangle with 2 equal sides.