Acceptable? It's for victim to decide (2,2,3,4)

I believe the answer is:
up to the mark
'decide' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'acceptable? it's for victim' is the wordplay.
I cannot quite understand how this works, but
'acceptable?' could be 'u' (as in U and non-U speech) and 'u' is located in the answer.
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is found within the answer.
'victim' could be 'mark' (mark is a kind of victim) and 'mark' is located in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is located in the answer.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
