Maigret playing Joplin's sort of music (7)
I believe the answer is:
ragtime
'joplin's sort of music' is the definition.
(sort of music composed by Scott Joplin)
'maigret playing' is the wordplay.
'playing' indicates anagramming the letters.
'maigret' is an anagram of 'RAGTIME'.
(Other definitions for ragtime that I've seen before include "Syncopated piano music - migrate (anag)" , "Jazz music for Maigret" , "Style of jazz popularised by Scott Joplin et al" , "Early jazz style" , "Style of piano music" .)