Again it's too much (4)
I believe the answer is:
Here is my best explanation:
This clue is a double definition.
'again' is the first definition.
(as in the phrases 'start over' and 'start again')
'too much' is the second definition.
(I've seen this in other clues)
'it's' is the link.
(Other definitions for over that I've seen before include "Finished like bowling session", "Finished, done", "balls > left", "Across", "Unit of test", "Directly above", "Remaining", "end to radio communication?", "Above; finished" and "bridge?".)