Disagreeable person's son taking our cat (8)
I believe the answer is:
sourpuss
'disagreeable person's' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?
'son taking our cat' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'taking' is a charade indicator (letters next to each other).
'cat' becomes 'puss' (puss is a kind of cat).
's'+'our'+'puss'='SOURPUSS'
Can you help me to learn more?
(Other definitions for sourpuss that I've seen before include "One has a habitually sullen expression" , "Bad-tempered person" , "Habitually sullen person" , "Sullen-looking person" , "Habitually gloomy person" .)