Not many people with a dog will keep one indoors (6)
I believe the answer is:
curfew
'will keep one indoors' is the definition.
I can't judge whether this defines the answer.
'not many people with a dog' is the wordplay.
'not many people' becomes 'few' (I can't explain this - if you can you should believe this answer much more).
'with' is a charade indicator (letters next to each other).
'a dog' becomes 'cur' (both can mean a despicable person).
'few' put after 'cur' is 'CURFEW'.
Can you help me to learn more?
(Other definitions for curfew that I've seen before include "Night-time deadline" , "Regulation restricting movement at night" , "restraining order" , "Restriction on nocturnal movement" , "It requires people to be indoors during certain hours" .)