Transit (7)
'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" .)