I made a script that clones a part named outerB. The part is then inserted into a folder called debris which is in the Workspace. After that the part is then teleported to the player and is slowly resized; but thats where the problem starts, resizing. When the part gets resized it gets resized on both sides instead of one.
outerB.Parent = game.Workspace:findFirstChild('Debris')
outerB.CFrame = root.CFrame*CFrame.new(0,0,-10)
outerB.CFrame = outerB.CFrame*CFrame.Angles(80.1,0,0)
innerB.Parent = game.Workspace:findFirstChild('Debris')
innerB.CFrame = root.CFrame*CFrame.new(0,0,-10)
innerB.CFrame = innerB.CFrame*CFrame.Angles(80.1,0,0)
for i = 0.5,15 do
wait()
outerB.Size = outerB.Size + Vector3.new(0.5,i,0.5)
innerB.Size = innerB.Size + Vector3.new(0.25,i,0.25)
end

3 comments
You cam move the part slightly to where you want the one side to be resized. I hope this works!
As hiimgoodpack suggested, You can move move the object as while as resizing it, so it will seems as if it is resizing in only one direction.
That doesn't seem to work