Jazz fans taking prison examination (3,4)
I believe the answer is:
cat scan
'examination' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'jazz fans taking prison' is the wordplay.
'jazz fans' becomes 'cats' (I've seen this in another clue).
'taking' says to put letters next to each other.
'prison' becomes 'can' (the can is American slang for prison).
'cats'+'can'='CAT SCAN'
Can you help me to learn more?
(Another definition for cat scan that I've seen is " Three dimensional image".)