Standards or principles on which to base a judgement (8)
I believe the answer is:
criteria
I believe this clue is a double definition.
'standards' is the first definition.
(I know this)
'principles on which to base a judgement' is the second definition.
(I've seen this before)
(Other definitions for criteria that I've seen before include "'Standards, reference points (8)'" , "Standards by which judgement can be made" , "Benchmarks" , "Ideals" , "Principles for decision" .)