Add a new storey to provide cheer (5,3,4)
I believe the answer is:
raise the roof
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for raise the roof that I've seen before include "Extend the house" , "Make a great noise" , "work on loft extension?" , "cause a massive disturbance?" , "Make tremendous commotion" .)