Over time, state becomes mean (7)
I believe the answer is:
average
'mean' is the definition.
(synonyms)
'over time state' is the wordplay.
'over' is a charade indicator (letters next to each other).
'time' becomes 'age' (age is a kind of time).
'state' becomes 'aver' (I've seen this before).
'age' after 'aver' is 'AVERAGE'.
'becomes' acts as a link.
(Other definitions for average that I've seen before include "It's common" , "Mean figure?" , "Mediocre - medium" , "Mediocre, commonplace" , "Arithmetically ordinary?" .)