Cat sat by cold and appreciative house-sitter (7)
I believe the answer is:
clapper
'cold and appreciative house-sitter' is the definition.
I can't judge whether this defines the answer.
'cat sat by' is the wordplay.
'cat sat' becomes 'clap' (I am not sure about this - if you are sure you should believe this answer much more).
'by' becomes 'per' (I've seen this in another clue).
'clap'+'per'='CLAPPER'
Can you help me to learn more?
(Other definitions for clapper that I've seen before include "Bell's tongue" , "The tongue or striker of a bell" , "One heartily greeting another" , "Bell hitter" , "appreciative person" .)