Here's why:
* Solid often describes something that is strong, durable, and dependable.
* Resident citizen refers to someone who lives in a place and has the legal rights of a citizen.
Putting it together, "solid resident citizen" suggests a person who is a reliable and trustworthy member of their community. They are likely someone who has been living there for a long time, is well-respected, and contributes positively to the area.