It's easy to be so idle (10)
I believe the answer is:
effortless
'it's easy' is the definition.
(associated in meaning)
'to be so idle' is the wordplay.
I cannot quite see how this works, but
'to' could be 'for' and 'for' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for effortless that I've seen before include "a breeze?" , "Requiring no physical or mental exertion" , "Not showing any strain" , "easy" .)