Where Jack might end up sounds unacceptable (6,3,4)
I believe the answer is:
beyond the pale
'unacceptable' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for beyond the pale that I've seen before include "Not understood by untanned people" , "completely washed out?" , "Outside limits of social convention" , "Morally or socially intolerable" , "Outside the bounds of acceptable behaviour" .)