For instance, newspapers, radio and TV service – main sources of information apparently (4,5)
I believe the answer is:
mass media
'for instance newspapers' is the definition.
(I know that newspaper is a type of publisher)
'service main sources of information apparently' is the wordplay.
'service' becomes 'mass' (church service).
'main' becomes 'med' ('main' can mean the sea - eg Mediterranean or Med).
'sources of' suggests taking the first letters (the beginning of a word is its sauce).
The first letters of 'information apparently' is 'ia'.
'mass'+'med'+'ia'='MASS MEDIA'
'radio and tv' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for mass media that I've seen before include "Press, TV, etc" , "Newspapers, TV etc" , "Papers, TV, radio, etc" , "Agencies of public information" , "Means of communication reaching large numbers" .)