Clue: Flinch from Arthur, in a fix (4,1,4)
Answer: TURN A HAIR
Explanation: Flinch from Arthur, in a fix (4,1,4)
This became a little easier when I read the first word as it was printed, not as 'filch'. It is an anagram ('fix') of 'Arthur in a', and the definition is more commonly seen in the negative NOT TURN A HAIR, meaning 'do not filch'. Or something.