Music created by jazz aficionado wearing new coat (7)
I believe the answer is:
toccata
'music' is the definition.
(toccata is a kind of music)
'jazz aficionado wearing new coat' is the wordplay.
'jazz aficionado' becomes 'cat' (I've seen this in another clue).
'wearing' means one lot of letters goes inside another.
'new' indicates an anagram.
'coat' anagrammed gives 'toca'.
'cat' placed inside 'toca' is 'TOCCATA'.
'created by' acts as a link.
(Other definitions for toccata that I've seen before include "lively piece" , "technical challenge" , "Musical composition for keyboard to show technique" , "Keyboard composition emphasising technique" , "High-speed keyboard piece" .)