Start of a song (5)
I believe the answer is:
intro
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">start of a song</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for intro that I've seen before include "Prologue, opening (abbr.)" , "starter" , "First notes" , "Opener" , "Prelude" .)