Oaf, I understand, enthralled by the sound of you (5)
I believe the answer is:
yahoo
'oaf i understand enthralled' is the definition.
I can't tell whether this defines the answer.
'by the sound of you' is the wordplay.
'by' says to put letters next to each other.
'the sound of' becomes 'hoo' (I can't justify this - if you can you should give a lot more credence to this answer).
'you' becomes 'ya' (non-standard spelling as in 'see ya later').
'hoo' put after 'ya' is 'YAHOO'.
Can you help me to learn more?
(Other definitions for yahoo that I've seen before include "Brutal lout" , "Brutish lout" , "Brute; hurrah" , "Coarse type" , "Uncouth person" .)