Jazzy, so bluesy, I'm so grateful (5,3)
I believe the answer is:
bless you
'i'm so grateful' is the definition.
I know nothing about this answer so I can't tell whether this works.
'jazzy so bluesy' is the wordplay.
'jazzy' is an anagram indicator.
'so'+'bluesy'='sobluesy'
'sobluesy' is an anagram of 'BLESS YOU'.
Can you help me to learn more?
(Other definitions for bless you that I've seen before include "often follows sudden explosion!" , "Traditional saying to person who has sneezed" , "Words said to a sneezer" , "Thanks a lot!" , "Response to sneeze" .)