Italian tenor standard (1,4,3)
I believe the answer is:
o sole mio
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">italian tenor standard</span>' is the definition.<br/ ><span class="explanation-format__explanation">(well-known Neapolitan song written in 1898)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for o sole mio that I've seen before include "Italian tune" , "Italian original of Presley's It's Now or Never" , "Neapolitan song" , "Italian song anglicised as It's Now or Never" , "Air" .)