Maigret's sort of music? (7)
I believe the answer is:
ragtime
'music?' is the definition.
(ragtime is a kind of music)
'maigret's sort' is the wordplay.
'sort' is an anagram indicator.
'maigret' with letters rearranged gives 'RAGTIME'.
'of' is the link.
(Other definitions for ragtime that I've seen before include "musical style" , "Syncopated music genre" , "Maigret (anag)" , "Syncopated jazz style" , "Syncopated music style" .)