Regarded as having taken no active part (6,2)
I believe the answer is:
looked on
'regarded' is the definition.
(I've seen this in another clue)
'taken no active part' is the wordplay.
I cannot quite understand how this works, but
'no' could be 'o' (O resembles 0) and 'o' is located in the answer.
'active' could be 'on' (I've seen this in other clues) and 'on' is found within the answer.
This explanation may well be incorrect...
'as having' acts as a link.
Can you help me to learn more?
(Another definition for looked on that I've seen is " Watched".)