Turned on by Irish film genre (4)
I believe the answer is:
noir
'film genre' is the definition.
(film noir)
'turned on by irish' is the wordplay.
'turned' says the letters should be written in reverse.
'by' means one lot of letters go next to another.
'irish' becomes 'IR' (abbreviation for Irish).
'on' backwards is 'no'.
'no'+'ir'='NOIR'
(Other definitions for noir that I've seen before include "type of film" , "(Of film or fiction) with bleak settings and cynical characters" , "Dark in France, like brooding films of 40s and 50s" , "cinematic style" , "Kind of dark film" .)