Tumbledown shack (5)
I believe the answer is:
hovel
'tumbledown shack' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hovel that I've seen before include "Ramshackle dwelling" , "A wretched little dwelling" , "Shanty; hut" , "Grubby tumbledown dwelling" , "Squalid dwelling" .)