### Clue: European royal family to come down on one British monarch (7)
### Answer: RAINIER 
 ### Explanation: Definition: European royal family
 RAIN(to come down in large quantities) **placed above**(to come down on, in a down clue) I(Roman numeral for "one") + ER(abbrev. for Elizabeth Regina, the current British monarch).**
Defn: … in Monaco.