Clip speed is not a regular parameter, it doesn't have animations at this time.
Here is the feature request about it, feel free to join the discussion viewtopic.php?t=20975
Software developer, Sound Engineer,
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You can hack this using Wire by creating a Float In for the Video Players Phase, but you would need to do this for each clip and that can take some time. If it's just for a few clips, this might be a solution for now.