Harriet’s relatively small cathouse? (5,4,5)
I believe the answer is:
uncle toms cabin
This might be a double definition.
'harriet's' is the first definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I can't see?
'relatively small cathouse?' is the second definition.
The definition suggests a singular noun which matches the answer.
(Other definitions for uncle toms cabin that I've seen before include "Volume" , "Anti-slavery novel" , "Harriet Beecher Stowe novel" , "Harriet's book" .)