Likely quietly to steal from clever people (8)
I believe the answer is:
probable
'likely' is the definition.
(I know that likely can be written as probable)
'quietly to steal from clever people' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'to steal from' becomes 'rob' (I've seen this in another clue).
'clever people' becomes 'able' (I can't justify this - if you can you should believe this answer much more).
'p'+'rob'+'able'='PROBABLE'
Can you help me to learn more?
(Other definitions for probable that I've seen before include "Likely to be the case" , "Like to happen" , "Person most likely" , "Likely to happen but not certain" , "on the cards" .)