Idolatrous virtuoso player, not popular one (5)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

“Paganini”(Niccolo, Italian virtuoso violinist) minus ( not ) [ “in”(popular/fashionable) + “I”(Roman numeral for “one”) ]. Answer: Worshipping idles, said of one who does not belong to any of the main organised religions.