Opening bars? (5)
I believe the answer is:
intro
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">opening bars?</span>' is the definition.<br/ ><span class="explanation-format__explanation">(opening bars of a piece of music)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for intro that I've seen before include "this may get one started" , "First bars of a musical composition" , "Song's first few bars" , "Opening bars of a song" , "Opening passage (abbr)" .)