### Clue: Setter's dog facing new attack (6)
### Answer: IMPUGN 
 ### Explanation: Definition: attack
 I'M(contraction of "I am"/"setter is"/setter's, using the self-referential pronoun) + PUG(a breed of dog) **plus**(facing) N(abbrev. for "new").
Defn: …/to challenge/to question.