Group of four musicians (7)
I believe the answer is:
quartet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">group of four musicians</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 quartet that I've seen before include "Group of four musicians" , "Two violins, viola and a cello string group" , "Stringed group" , "Four musicians playing together" , "Group such as the Beatles" .)