Scream after at least a dozen balls go too far (9)
I believe the answer is:
overshoot
'go too far' is the definition.
(to overshoot is to go past)
'scream after at least' is the wordplay.
'scream' becomes 'hoot' (hoot can mean to scream or cry).
'after' is a charade indicator (letters next to each other).
'at least' becomes 'overs' (I can't explain this - if you can you should give a lot more credence to this answer).
'hoot' after 'overs' is 'OVERSHOOT'.
'a dozen balls' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for overshoot that I've seen before include "Go past unintentionally" , "Go past the mark" , "Go extra distance" , "Taxi too much, perhaps" , "Go beyond the intended target" .)