cliquish
/ˈklɪkwɪʃ/Definitions
1. adjective
relating to or characteristic of a clique; having a tendency to form cliques or exclusive groups
“The school’s cliquish social hierarchy made it difficult for new students to fit in.”
2. adverb
in a way that is characteristic of a clique; in an exclusive or cliquish manner
“The party was cliquish, with most of the guests knowing each other from college.”