How do I make a chat regen script?

I'll answer it for you, one second, let me get on a PC to write it. Here you go:

model = game.Workspace.Thing --Change "Thing" to the model name you want respawned.
backup = model:clone() 

function onChatted(msg, recipient, speaker) 

local source = string.lower(speaker.Name) 
msg = string.lower(msg) 

if (msg == "thing") then --Change "thing" to the keyword you want to respawn the model with.
model = backup:clone() 
model.Parent = game.Workspace 
model:makeJoints() 
end 

end 

function onPlayerEntered(newPlayer) 
newPlayer.Chatted:connect(function(msg, recipient) onChatted(msg, recipient, newPlayer) end) 
end 

game.Players.ChildAdded:connect(onPlayerEntered) 

I do not understand the question. Do you mean it clears the chat log?