Sound vaguely familiar (4,1,4)
I believe the answer is:
ring a bell
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sound vaguely familiar</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for ring a bell that I've seen before include "Begin to rouse memory" , "jog one's memory" , "Signal to start class" , "may awaken memories" , "Recall" .)