The average first-class return can be viewed as informative, generally (5)
I believe the answer is:
media
'be viewed as informative generally' is the definition.
I can't tell whether this defines the answer.
'the average first-class return' is the wordplay.
'the average' becomes 'med' (I can't explain this - if you can you should give a lot more credence to this answer).
'first class' becomes 'ai' (Am - top quality).
'return' is a reversal indicator.
'ai' backwards is 'ia'.
'med'+'ia'='MEDIA'
'can' is the link.
Can you help me to learn more?
(Other definitions for media that I've seen before include "Old Asian region" , "Mass communications" , "Oil etc" , "Vehicles" , "the box etc" .)