____ transit (4)
'transit' is the definition.
(I know that transit can be written as passage)
This is all the clue.
(Other definitions for passage that I've seen before include "Transit - part of book etc" , "Channel" , "Way through; sea journey" , "Sea/air journey" , "crossing" .)
(Other definitions for mass that I've seen before include "Church service - crowd" , "Holy service" , "Religious rite" , "Rite; quantity of matter" , "Matter; large amount" .)