Cool to check out music genre (5)
I believe the answer is:
indie
'music genre' is the definition.
'cool to check out' is the wordplay.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'to' is a charade indicator (letters next to each other).
'check out' becomes 'die' ('check out' can informally mean to die).
'in'+'die'='INDIE'
(Other definitions for indie that I've seen before include "(In films or music) group not linked to a major company" , "Type of music" , "Autonomous film co." , "Kind of small record company" , "minor label" .)