why does this short script not work?

What your issue is line 4. The variables being set to local won't change much. I'm trying to understand what you're trying to accomplish. You're either a: Trying to clone 1 tool into the player's backpack b: Trying to clone a set of tools into the player's backpack Since it's hard to tell which you're going for, I'll offer both solutions.

Solution A:

btn1 = script.Parent
player = game.Players.LocalPlayer

btn1.MouseButton1Down:connect(function()
    game.Lighting.tools.Dribbler:clone().Parent = player.Backpack
end)

Solution B:

btn1 = script.Parent
player = game.Players.LocalPlayer

btn1.MouseButton1Down:connect(function()
    for i,v in pairs(game.Lighting.tools.Dribbler:GetChildren()) do
        v:clone().Parent = player.Backpack
    end
end)

Any questions? Feel free to comment!

You're trying to set a Table's parent. You can't do that.

In order to set all the Children's Parent, you need to set a Generic For loop, something like this:

for _,v in pairs(game.Lighting.tools.Dribbler:GetChildren()) do
    v:Clone().Parent = player.Backpack
end

Also, I'd recommend using game.ReplicatedStorage instead of game.Lighting. Using game.Lighting as an asset storage is deprecated.

Perhaps set the variables as local variables like so

local btn1 = script.Parent
local player = game.Players.LocalPlayer
btn1.MouseButton1Down:connect(function()
game.Lighting.tools.Dribbler:GetChildren().Parent = player.Backpack
end)