Vibrating part of some instruments (4)
I believe the answer is:
reed
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">vibrating part of some instruments</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for reed that I've seen before include "'It vibrates in a clarinet, say (4)'" , "Type of musical instrument" , "Grass of marshes" , "Oliver perhaps" , "Tall water-loving grass" .)