### Clue: is one, say, in downward movement (10)
### Answer: RELEGATION 
 ### Explanation: Definition: downward movement 
 RELATION(of which, a sister/answer to 18 down is one/an example) **containing**(…, in) EG(abbrev. for "exempli gratia"/for example/say).
Defn: … from an upper rank/position to a lower one.