Either way it is unacceptable (3,2)
I believe the answer is:
not on
This clue is a double definition.
'either way' is the first definition.
'unacceptable' is the second definition.
(something 'not on' is unacceptable or frowned upon)
'it is' is the link.
(Other definitions for not on that I've seen before include "Informally, can't be accepted or tolerated" , "Colloquially, cannot be tolerated or accepted" , "Modern phrase for unacceptable" , "Improper - impossible" , "Unacceptable (colloq.)" .)