After service, aimed to change major communicators (4,5)
I believe the answer is:
mass media
'communicators' is the definition.
(I've seen this before)
'after service aimed to change major' is the wordplay.
I cannot really see how this works, but
'service' could be 'mass' (kind of church service) and 'mass' is present in the answer.
an anagram of 'aimed' is 'media' which is within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for mass media that I've seen before include "Papers, TV, radio, etc" , "TV, radio, press" , "Press, TV, etc" , "Agencies of public information" , "Communicators" .)