Quadrille (7)
I believe the answer is:
lancers
'quadrille' is the definition.
(lancers is a kind of quadrille)
This is all the clue.
(Other definitions for lancers that I've seen before include "Quadrille for eight/sixteen pairs" , "Cavalrymen; quadrille" , "Cavalrymen - dance" , "People performing opening acts in theatre" , "Old regiment; dance" .)