Marched en masse (7)
I believe the answer is:
trooped
'marched en masse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for trooped that I've seen before include "Went as a body" , "Paraded" , "Moved in a body, like soldiers with colours" , "Marched in a procession" .)