Organ piece for Charlie, jazz fan, No 1 in America (7)
I believe the answer is:
toccata
'organ piece' is the definition.
'toccata' can be an answer for 'piece' (toccata is a kind of piece). I am not sure about the 'organ' bit.
'for charlie jazz fan no 1 in america' is the wordplay.
'for' becomes 'to' (eg both can mean 'in the opinion of').
'charlie' becomes 'C' (phonetic alphabet: alpha, bravo, charlie etc.).
'jazz fan' becomes 'cat' (slang term for a jazz fan).
'no 1 in america' becomes 'a' (1st letter of 'america').
'to'+'c'+'cat'+'a'='TOCCATA'
Can you help me to learn more?
(Other definitions for toccata that I've seen before include "Flashy piece of music" , "Musical work designed to show player's technique" , "Touching piece" , "Musical composition for keyboard to show technique" , "Keyboard piece emphasising touch" .)