As far as "a dud on evil bent" (2,2,2,4)
I believe the answer is:
up to no good
'evil bent' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'as far as a dud' is the wordplay.
I cannot quite see how this works, but
'as far as' could be 'upto' ('up to' and 'as far as' can both mean 'until') and 'upto' is found in the answer.
The remaining letters 'nogood' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'on' is the link.
Can you help me to learn more?
(Other definitions for up to no good that I've seen before include "Scheming to do wrong(2.2.2.4)" , "Doing something mischievous" , "Making mischief" , "Doing something wrong" , "Misbehaving" .)