### Clue: Very enthusiastic about England footballer with unknown deficiency being abandoned (8)
### Answer: MAROONED 
 ### Explanation: Definition: abandoned
  MAD(very enthusiastic about/over) **containing**(about) ROONE{"Rooney"(Wayne, England footballer) **minus**(with … deficiency) "y"(one of the symbols in maths for an unknown quantity, overshadowed by its sibling, "x")}.