Learned rubbish mostly over time (8)
I believe the answer is:
literate
'learned' is the definition.
(able to read and write)
'rubbish mostly over time' is the wordplay.
I cannot quite understand how this works, but
'time' could be 'era' (era is a kind of time) and 'era' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for literate that I've seen before include "Well-read" , "Scholarly" , "properly educated" , "version of 'speed of light'?" , "Erudite" .)