There's always one note that's awesome (5)
I believe the answer is:
'awesome' is the definition.
'there's always one note' is the wordplay.
'there's' means one lot of letters go next to another.
'always' becomes 'eer' (poetic way of saying ever).
'one' becomes 'i' (Roman numeral).
'note' becomes 'e' (musical note).
'eer' next to 'i' is 'eeri'.
'that's' is the link.
(Other definitions for eerie that I've seen before include "Strange, frightening" , "Scary, weird" , "spine-chilling" , "Awesome" , "Spooky, creepy" .)