Sides with top class pitch (4)
I believe the answer is:
toss
'pitch' is the definition.
('toss' can be a synonym of 'pitch')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for toss that I've seen before include "'Flip, a coin or pancake say (4)'" , "Pitch" , "have a restless night, perhaps" , "Launch" , "Ditch" .)