Conservative crank, for instance, is cunning (6)
I believe the answer is:
clever
'is cunning' is the definition.
(synonyms)
'conservative crank' is the wordplay.
I cannot quite understand how this works, but
'conservative' could be 'c' (UK political abbreviation) and 'c' is present in the answer.
The remaining letters 'lever' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'for instance' acts as a link.
Can you help me to learn more?
(Other definitions for clever that I've seen before include "Gifted" , "Adroit, ingenious" , "Intelligent - skilful" , "Highly intelligent" , "Smart or shrewd" .)