Mass movement (6)
I believe the answer is:
gloria
'mass movement' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gloria that I've seen before include "Hymn of praise" , "sung in church" , "piece of church music" , "Prayer: '... in excelsis Deo'" , "Latin hymn: ''. . . . . . in excelsis Deo''" .)