Waiting for mass (7)
I believe the answer is:
service
I believe this clue is a double definition.
'waiting' is the first definition.
(I've seen this before)
'mass' is the second definition.
(mass is a type of church service)
'for' acts as a link.
(Other definitions for service that I've seen before include "Armed force - assistance" , "army, say" , "Set of matching crockery" , "Religious ceremony" , "start of action in court" .)