Form of modern music with true playing bringing great joy (7)
I believe the answer is:
rapture
'great joy' is the definition.
(rapture is a state of bliss)
'form of modern music with true playing' is the wordplay.
'form of modern music' becomes 'rap' (musical genre).
'with' is a charade indicator (letters next to each other).
'playing' indicates an anagram.
'true' anagrammed gives 'ture'.
'rap'+'ture'='RAPTURE'
'bringing' is the link.
(Other definitions for rapture that I've seen before include "transport" , "Extreme delight" , "Transports of delight" , "modified for Nanki-Poo?" , "Exaltation" .)