Easily grasped by many a listener (5)
I believe the answer is:
clear
'easily' is the definition.
Both the definition and answer are adverbs. Perhaps there's an association between them I don't understand?
'grasped by many a listener' is the wordplay.
'grasped by' becomes 'c' (I can't explain this - if you can you should give a lot more credence to this answer).
'many' becomes 'l'.
'a listener' becomes 'ear' (body part which hears or listens).
'c'+'l'+'ear'='CLEAR'
Can you help me to learn more?
(Other definitions for clear that I've seen before include "Lucid; to empty" , "Transparent, easy to see through" , "Plainly" , "Empty - vault" , "Obvious; remove obstructions from" .)