### Clue: Fly useful in these rivers to halve odds in Test (8)
### Answer: TROUSERS 
 ### Explanation: Definition: Fly useful in these
 [ R(abbrev. for "river") + OUSE(another river, this one in Yorkshire, England) + R(abbrev. for "river") ] **contained in**(to halve) **the 1st and 3rd letters of**(odds in) "Test ".
Defn: What a zipped or buttoned fly would be useful in.