Rascal notes hamper (6)
I believe the answer is:
impede
'hamper' is the definition.
(I've seen this before)
'rascal notes' is the wordplay.
'rascal' becomes 'imp' (synonyms).
'notes' becomes 'ede' (I can't explain this - if you can you should believe this answer much more).
'imp'+'ede'='IMPEDE'
Can you help me to learn more?
(Other definitions for impede that I've seen before include "Delay; block progress of" , "Put obstacle in the way, hinder" , "Obstruct, hold up progress" , "Delay or obstruct" , "Stand in the way of progress" .)